There are some really great videos of nerdy music on youtube done a cappella. Some of them, particularly the ones where it's the same guy doing each part, are really good. If you haven't seen any of these, they're really worth checking out.
Especially this one, a Star Wars/John Williams tribute. Originally it was done by the a cappella comedy music group Moosebutter, and then it was rerecorded with permission by Corey Vidal. Here's the Vidal version:
I have to wonder if he was as excited about Episode I after he saw it.
This is a more recent video of the theme from the Legend of Zelda video game. This guy has a lot of hats. I like the extra heads that float across the screen and the violin was very well done. This makes me want to bust out the Super Nintendo and play some Link to the Past (arguably the best Zelda game out there).
Then there's a whole Nintendo compalation. This also makes me want to play some Mario, but not as much as I'd spend a few hours playing Zelda right now. I also like how Mortal Kombat is thrown in and the guy shouting "MORTAL KOMBAT!" which is essential to the Mortal Kombat theme.
My appologies to Eric if this was to be the subject of one of his upcoming blog posts. :)