Rifftrax is the logical extension of -and spiritual successor to- MST3k.
Mike Nelson, Kevin Murphy, and Bill Corbett (Mike, Servo and Crow, respectively) are back to riffing movies, this time as themselves. Instead of riffing on cheesy, generally obscure movies like they did on the show, though, they're now riffing on any movie they damn well please (or that their fan base won't stop bugging them about), including big budget Hollywood flicks that the studio would never have allowed them to do on MST3k.
The Rifftrax themselves are in audio format. They are meant to be purchased from the official site, then synced up to the movie of choice (usually through playing the MP3 and the DVD with whatever you have on hand).
Along with the original three actors, there's an almost-character named Disembaudio, who is the only robot involved. His main function is to introduce the riffs, randomly say a line of dialogue from the movie (to ensure you're synced up), and occasionally interact with the Riffers. They've also had a few guest riffers, including (but not limited to) Jonathan Coulton, Neil Patrick Harris, and Weird Al Yankovic.
Some (but not all) of the movies they've riffed:
* Batman And Robin
* Battlefield Earth
* The Bourne Identity
* Casino Royale
* The Dark Knight
* The Day After Tomorrow
* Drag Me To Hell
* Fantastic Four
* Rise of the Silver Surfer
* The Room
* Fast & Furious
* The Happening
* The first four Harry Potter films
* I Am Legend
* Independence Day
* Iron Man
* Paranormal Activity
* Peter Jackson's The Lord Of The Rings movies
* Pirates Of The Caribbean: The Curse Of The Black Pearl
* Raiders Of The Lost Ark
* Kingdom Of The Crystal Skull
* Reign Of Fire
* Star Trek
* Star Wars episodes one through six
* Transformers: Revenge of the Fallen
* Troll 2
* Twilight: New Moon
* The Wicker Man
* Willy Wonka And The Chocolate Factory (1971; with guest riffer Neil Patrick Harris)
* All three of the Matrix movies
Everything they do is funny.
Don't believe me? Here's a compilation of various quotes organized by movie. You can also find ten minute long "Best of Rifftrax -insert movie here-" videos on youtube put up by fans.
During one of the 300's many battle scenes:
Delios: ...What we were born to do.
Bill (impersonating Delios): What we were cast, costumed, and choreographed to do.
Mike (impersonating Delios): What we were blue-screened and digitized to do.
Bill (impersonating Delios): What we were shaved to do.