As previously mentioned on Metafilter, in 2006, the Kersal Massive, 3 English chavs from Kersal near Manchester made a 44 second rap video on a cell phone (click this one first).
Once it hit YouTube, it inspired parodies and mashups ranging from heavy metal to alternative to dancefloor, an acoustic cover version, a conspiracy theory video, a Kevin Powder interview , and best of all this version. But this one is my favourite.
posted on May 17, 2008 - View this thread

Santastic I, II, and now III, holiday mash-ups, alternate treatments and bootleg remixes.
Previously
posted on Dec 5, 2007 - View this thread

Cracked Pepper by ccc and ill chemist is a mash-up of The Beatles' Sgt. Pepper's Lonely Hearts Club Band and an amazing array of songs you know. While not quite on par with the focus and sheer audacity of DangerMouse's Grey Album, Cracked Pepper is a smart, rich, and rewarding listen. Available track by track or as a torrent. See inside for tracks sampled.
posted on Jul 30, 2007 - View this thread

The Hood Internet has a bunch of awesome remixes of hip-hop and indie rock(usually). I particularly enjoy R. Kelly vs. Broken Social Scene, Justice Vs. Destiny's Child, and Ghostface Killah vs. Spoon. I've been listening all morning.
posted on May 23, 2007 - View this thread

You like-a da mashups? Here, I give you mashups (about 40 of them to be exact).
posted on Jul 20, 2005 - View this thread

Grey Video: a further experimental mashup (this time, in video) of the Beatles and Jay Z, for the DJ Dangermouse song Encore. Looks almost as slick as the old Weezer Happy Days video by Spike Jonze.
posted on Nov 16, 2004 - View this thread

"We wanted to be the store that your mother didn't want you to go to." Cult band leader Dale Lawrence covers the RIAA shutdown of an Indianapolis record store, Berry's Music, for "Selling DJ mix-CDs.". Lawrence has written about mashups for a few years now. Is he also a deejay?
posted on Jul 28, 2004 - View this thread

The Slack Album The Slack Album is the latest (for the next ten minutes) in a slew of Jay-Z Black Album remixes and mash-ups. In this case, the Black Album is melded track-for-track with samples taken from Pavement's 1991 lo-fi / indie classic Slanted and Enchanted.
posted on Apr 29, 2004 - View this thread