The Nico Nico Douga 2007 medley (the Kumikyoku) was a little dance medley of anime / game themes, and was kinda cute but wasn't anything you'd want to withstand more than once.
Someone's made a hugely superior cover version as an instrumental using traditional Japanese instruments. I love it; I've been listening to it all day yesterday. It's great. Go listen:
http://www.youtube.com/watch?v=DqpmUkFn91M
The medley includes a load of stuff - Idolm@ster, GONG (SRW alpha 3), Haruhi, Madlax, Digimon, Busou Renkin, Air, Okusenman (Rockman 2 Wily Stage 1 theme), Lucky Star, Super Mario World, Dragon Quest, Final Fantasy epilogue etc. It's cool. ^_^
