This page is in no particular order, but is organized into groups according to series:
Sonic X
SatAm Sonic
Adventures of Sonic
Sonic Underground

Despite lacking a cover photo (there is one on the interior page if you actually click this) this is the semi-collectable DVD Double Shot. There were quite a few of these made, though they don't make much sense. There's only 2 episodes per disk and so for the price, you're better off doing ANYTHING else.
However their slimline plastic cases and art put them in somewhat minor demand. There also aren't too many of these around any more. (When people realized that they could do better with the regular episode disks for the dollar, sales dried up, naturally) This is listed here more as a novelty, and to show that it exists rather than anything else. The only episodes are listed in its' title, so it's easy to see it's about 1 hour with no bonuses.

This series of disks is what you'd have if you started buying Sonic X from the beginning when it was first released. (Also in the SonicGear personal collection) They were throwing out several episodes PLUS a "Bonus Episode" on individual boxed disks. Do not be misled by the "Bonus Episode" because what they've done is pull a random ep. from later on in the series and throw it on out of order. If you want to see the show in it's proper order, do not watch the extra episode. The bonuses for this disk include character bios and some of X's commercials. This is about 80 minutes long, and comes in a hard plastic case with the art you see here.
1. Chaos Control Freaks
2. Sonic to the Rescue
3. Missile Wrist Rampage
4. Pure Chaos (this is from season 2)

This one too is 80 minutes long and contains the following episodes: Satelite Swindle,The Last Resort,Unfair Ball, & Fly Spy. For this, they list FlySpy as the bonus episode, but really again, it isn't. Rouge the Bat first appears in that episode and later teams up with Agent Topaz in the series.

This was 10.99 if you bought it in stores when it first came out. This is in the SonicGear personal collection.

This is not usually "listed" as 'vol 4' but it is. This is the first disk to be 100 minutes long, which means it has another whole episode on it. It has "Beating Eggman" parts 1 and 2., as well as:
Thats what friends are for
Skirmish in the Sky
Depths of Danger

This time the last 2 episodes are called bonuses, and no other bonus items are included.

This one's a little longer, at 100 minutes of show time. They've stopped calling regular episodes 'bonuses' which is good and sure to result in somewhat less confusion by buyers. This particular set of episodes are not particularly vital to the plot, but some are supposed to contain more comedy elements. With this disk you get The Adventures of Knuckles and Hawk, The Dam Scam, Sonic's Scream Test, Cruise Blues and Fast Friends. The title of the disk and one of the episodes is the same and is clearly a play on "Screen Test" which is a movie term. Though a pun, it is a bit fitting for the episode which has king BoomBoo in it, who you will remember from the games.

This ones' a little longer, clocking in at about 100 minutes of show time. It has 2 so called bonus episodes, which add to its' runtime. Again, they're not really bonuses, they're just selecting things from later on in the series.
Little Chao Lost - Eggman thinks Chris and friends found another Emerald. He unleashes E-66 which sets off an environmental disaster
Emerald Anniversary - Chris' dad tries to give his mom the sixth Chaos Emerald as a gift but it is swiped by Eggman.
How To Catch A Hedgehog - Chris and Chuck must figure out what is keeping Sonic's legs running at all times before he runs himself ragged.
BONUS EPISODE: A Dastardly DeedKnuckles calls a truce with Eggman and convinces Chris to give up all their Chaos Emeralds. Will Eggman live up to his end of the bargain?
BONUS EPISODE: Countdown to ChaosA mysterious island appears when the seventh emerald drops into the water along with Eggman's emeralds.

This one is still 100 minutes and has episodes 27-32. It's a somewhat-re-telling of Sonic Adventure 1, with Chaos appearing and going on a rampage. If you liked the game, you'll likely go for this arc as well. No bonuses appear here, either.

130 Shadow-centric minutes in this set of episodes. This is a rather exciting and game-based arc of episdoes. Still, the cutting of this USA version is fairly strong here, so again, if you get this be sure to check the internet for what was lost. This disk is in the SonicGear personal collection and contains the following episodes:
Project Shadow
Shadow Knows
Sonic's Big Break
Shadow World
Showdown in Space
Robotnik's Revenge

A longer one, at 130 minutes. This one has no episode list and no mention of bonuses. This was one that was more difficult to find in stores for some reason. Likely because it appeared right before they decided to do 'seasonal sets', which by their existance phased out these lower-volume disks. If you own this and know what episodes are on it, write in for credit.

The longest one, clocking in at 170 minutes of show time with 8 episodes. Still, it doesn't list which ones are on the disk, or if there are any bonuses. This one is harder to find in stores than volume 9, and was the last one of this type produced. If you own this and know what episodes are on it, write in for credit.

For description, one can only go by what's visible and previously known here, which is that it's likely a few (but how many?) SatAM episodes, possibly set up out-of-order. The problem would be that the show did have continuity and rather needed to be watched in-order for it to make sense. The cover has some slightly modified art (Sonic w/world) but it doesn't really give anything away.

A single dvd with 88 minutes worth of shows. This is the SatAm series. With this you get Hooked on Sonics, Ultra Sonic, Warp Sonic and Sonic and Secret Scrolls. Most notably out of the episodes, Secret Scrolls had a lot of hype in its day because it involved Floating Island...but it was JUST A floating island, and had nothing to do with Knuckles/Angel Island etc. There are 0 bonuses on this disk.

Another 88 minute disk. Interestingly, despite the title, it does not contain Super Sonic. Super Sonic never appears in SatAm show. However, there is an episode named "SS" just because they were going through all the regular english words that "Sonic" appears as part of, for their episode titles. This disk contains the following episodes:
Sonic Boom,
Sonic & Sally,
Sonic Racer,
Super Sonic.
There are 0 bonuses on this disk.

This is an 88 minute set of the AoStH episodes. The cover reveals it with the title, but uses a more "sat am" style Robotnik, so don't be fooled. This has High Stakes Sonic, Sonic Song, So Long Sucker, and Pseudo Sonic. (Pseudo Sonic is the one with a "Metal Sonic-Robot" appearing in it, but it's like the one in Sonic 2 rather than Sonic CD) There are 0 bonuses on this disk.

For this 88 minute set they have chosen "Tails-centric" episodes and compiled them into a DVD for Tails fans. That didn't help the mis-colored sort of poorly adapted Tails stock art on the cover though. With this disk you get:
Trail of the Missing Tails - When Tails gets trapped in the Warp of Confusion by Robotnik's cousin, Sonic comes to the rescue and traps Robotnik and his badniks in the warp.
Too Tall Tails - Tails gets a mega-dose of Robotnik's growth gas and grows quickly to monstrous proportions, eating everything in sight. Sonic must find the antidote and get it to Tails before Robotnik can persuade the angry villagers to destroy Tails.
Tails New Home - When Sonic decides to find Tails a suitable foster home, Robotnik creates a robot fox family which poses as Tails' long lost parents. Sonic leaves Tails with the fox family, but finally realizes they're robots and rescues Tails.
Tails in Charge - Sonic leaves Tails in charge of protecting a squirrel village food supply when he zips off to stop a dam from breaking. Robotnik sends Scratch & Grounder after Tails, who defends himself w/wacky booby traps. When Tails gets caught, Sonic speeds back to save him.

For this 88 minute set, they've chosen to spotlight the relatives of Robo. His robot son (who goes good, ironically) and his mom, who looks pretty much like a fatter version of him, but in a dress. She's an actual nuisance because she's pretty intelligent (for this show).
Momma Robotnik s Birthday- Robotnik's momma escapes from the home for mothers of villains, and demands her birthday present! When she endangers Sonic and Tails, and they manage to have her taken back to the home. Even Robotnik is glad to see her go.
Robotnik, Jr.- Robotnik plans to block out the sun & extinguish all life and nature on Mobius. He creates a robot son & tries to train him in the ways of wickedness. But when Robotnik Jr. meets Sonic, he becomes a naturalist & teams up with Sonic to thwart Robotnik's evil scheme.
Sonic the Matchmaker - Sonic plays Cyrano to bring Robotnik Jr. and Breezie together. The problem is, Breezie's crazy about Sonic. Sonic gets out of the way, but when he does, Junior is captured by Robotnik, and Breezie comes to the rescue, finally falling for him.
Momma Robotnik Returns -Momma escapes from the Mobius Home for Really Bizarre People, disowns Robotnik for failing to capture Sonic, then with the help of an obscure Mobius law, adopts Sonic! Sonic is miserable as a Cinderella hedgehog with Scratch and Grounder as the evil stepbots, till Robotnik and Coconuts find another obscure law which frees Sonic.

This is 154 minutes of the supposedly 'best' episodes from AoStH. Disk is NOT in the SonicGear Collection, it's true episode content is unknown in 2016. If you get this, write in for description credit.

Another themed compilation, likey as well 88 minutes however Amazon's not telling. This one can be a bit hard to find in its' search, so the button is rather convenient. Only speculation can come out here until someone actually owns it and writes in. It likely features some of Robotnik's specific robots like the anti-music-bot and possibly the bounty hunter robots or pseudo-Sonic.

While Sonic is most always the hero of this show, for this 88 minutes they've chosen episodes where they think it is more a theme than others. There are 0 bonuses. With this disk you get:
Over the Hill Hero - An elderly, out of shape superhero keeps trying to help Sonic battle Dr. Robotnik, and keeps getting him in more jeopardy.
Mass Transit Trouble - Robotnik decides to cripple Mobius' three major transit systems. Sonic has to circumnavigate the planet in order to save the day.
Robolympics - When Robotnik puts a meteor on a collision course with a village, Sonic is forced to compete in the Robolympics to save the village.
Mobius 5000 - Robotnik lures Sonic into a round-the-planet vehicle race by threatening to foreclose on a loan to an orphanage.

This is undoubtedly an episode mash-up where they selected the few that had to do with the Chaos Emerald/s. Knuckles also appears (For what little he did in the show) in each of the episodes. The first one introduces him, and the other 3 are a mini-arc with the emerald plot, and Knuckles does appear in each one. However, Amazon doesn't say the exact titles of which episodes are on this disk, though there are 88 minutes worth of them. Additional info by LuckyLadybug

They've chosen some Season 2-ish episodes for this, with Queen Aleena as a vague theme. Who is that? It's the 3 siblings' purple mother who mysteriously vanishes when Robotnik arrives on the scene after giving up her three children. This is about 88 minutes long and has the following episodes:
Wedding bell Blues,
To catch a queen,
The Jewel of the Crown
Country Crisis
So you know this entire show ended without anyone ever catching up to the queen because it was meant to be an eternal cliffhanger.

88 Minutes of something!
Sonic was usually coming to the rescue in this show too, so this could be literally any of the episodes. If you own this, write in for credit as to what exactly is on here. Amazon provides 0 explanation.

While only 76 minutes, this one has Sean Connery in it. He's an old echidna, which will certainly bring up memories of Archie Comics Knuckles' series too. One must wonder what they did to lure in such a famous actor onto such a nonsensical show as this? This DVD cover also has the mistake-art 'blue arms Sonic' for some reason. How did this pass inspection?

1.Beginnings
2.A hedgehog's home is her castle
3.Modoboon

Mystery Disk! (again)