If you don't know what Mystery Science Theater 3000 is, you need to find out!

Mystery Science Theater 3000 ran for ten seasons on channel KTMA, Comedy Central, and the Sci-Fi channel. It is the best in movie riffing.
I have acquired all of the episodes and am watching them in order. I first started watching on the Sci-Fi channel, so I have seen seasons 8-10 and some that I bought commercially. Now, I have watched season KTMA and 1-2 and am currently on season 3.
Most of the KTMA episodes are somewhat funny (not great) because they were really only making comments that related to the cheesy movie. Later on, they learned how to make completely irrelevant comments that about make you pee you pants.
If you're not a die-hard fan, I would recommend buying some of the later episodes first. They started getting really good at it in season 2, but all the episodes are worth watching.
Also, with season 1 and 2, a lot of the comments refer to previous movies, so you sort of have to watch them in order to get all the jokes. By the season three, they seemed to quit doing that.
Some of the best of the early episodes:
- The Crawling Eye
- The Crawling Hand
- Project Moonbase
- Robot Holocaust
- The Black Scorpion
- Rocketship X-M
- Wild Rebels ("that guy bugs me, he really bugs ME")
- Cave Dwellers **The best one so far, absolutely hilarious!!!
- Pod People - another really good one

And, of course, if you haven't seen The Movie, you should. It IS the best "episode" of them all.

Here is the official website:http://www.mst3k.com/

The official fan site:http://www.mst3kinfo.com/

All of the episodes that are commercially available you can get from Rhino or Shout! All of the out of print episodes you will have to find from another source.
I bought all of mine from what I consider to be the most dedicated MST3 fan. Except for KTMA (the earliest season), all of his episodes are pristine copies, but even the KTMA season are still very good copies. I am very pleased with my dvds. (Please PM me if you are interested in checking his stuff out. He also some other neat stuff like normal cheesy old movies, MST3 extras, etc.)

Check back and I will keep you posted on the episodes that are the funniest!
:p

There have also been two spinoffs from the same people that did MST3.

Rifftrax:http://www.rifftrax.com/content

Cinematic Titanic:http://www.cinematictitanic.com/

Both of these are worth checking into. I have seen a couple of dvds from Cinematic Titanic and they were pretty funny. Also a couple from Rifftrax and those are good too, especially the shorts (riffing those old public service ads and lame school instructional videos, like why you shouldn't cheat, etc.)

I just finished watching the MST3 episode of It Conquered the World (#311). OMG, this one was one of the best so far! The movie is atrocious of course, but they did an excellent job of riffing this one. There is also a short about snow activities that is frickin' hilarious! If you are MST3 fan, you should definitely check out this episode.:lol:

P.S. Probably THE worst movie monster in the history of crappy movies!!!

If you want a suggestion for Rifftrax, you must see Carnival of Souls. Holy hell, they did a good job of riffing that one! It is freakin' hilarious.

SPOILER: A thought about old "horror" movies. 

Something I find funny about it all is that the movie is a black and white (made in 1962) and it involves a young woman who is ghost but doesn't realize it. Now, after having seen so many good horror movies with more complicated plots (like the House on Haunted Hill remake with Geoffrey Rush and 13 Ghosts with Tony Shaloub), when I watch a movie like that, I say to myself: Okay, she's a ghost...and... But that's it. Oohh, scary.

Yet another entertaining installment in the MST3K series: "Space Travelers" (#401) aka "Marooned". The movie is awful, but Joel and the bots do an excellent job of riffing this one. Crow (Trace Beaulieu) does a perfect Gregory Peck, and most of his comments catch you off guard, so it is advisable to refrain from eating or drinking during the viewing of this one. I highly recommend MSTie fans get their hands on this episode.

Two more excellent episodes: "Atomic Brain" and "12 To The Moon"