We have the "prog on YouTube" threads, but they're meant to have only originals - and they're very good at that. Sometimes covers are also interesting for various reasons, like being ridiculous, inspiring, amazing, funny, creative, goofy, being your own version... Post videos (links I mean) and comment! Also, please include proto & related song. I'm gonna start with such one.
Here's what I found while documenting YouTube for the longer, more difficult songs from second era Zeppelin : two interesting versions of Achilles Last Stand that I'd like you to watch. The first ( http://www.youtube.com/watch?v=RzzTKukFPwg ) comes from some enthusiast guys that do a very good job; excellent amateur (?) drumming, considering the song's difficulty for drums, and the dude also sings! The second one ( http://www.youtube.com/watch?v=Gst_eAWu5t0 ) is also a good rendition; even tighter than the first one, but it's not that good of a recording. However, the amazing fact is that the band consisted of four kids having 13 to 15 years!
Coming to pure prog now, I think you'll enjoy this Brazilian version of Roundabout ( http://www.youtube.com/watch?v=orpLcjyjMOw ). It may show some reason for Erik's thread on South America as prog-leader. These guys are no amateurs!