I have a Rhapsody account (paid version) and there I have set up many folders for various themes (battle etc).
Rather than list out too much, I'll just put down a few...
1. Sherlock Holmes Sountrack
This one is pretty new of course. The soundtrack to the movie was great (the sound in general really) and much of this is perfect for games, especially quirky city themed stuff. I dig it. Here is a sample...
[ame]http://www.youtube.com/watch?v=6XG7ljnDC-I[/ame]
2. Rome Total War Soundtrack
This soundtrack came with the game and is amazing. I have used this many many times in games. It has stuff that can be used in various situations, not just battles, etc. Here is one sample...
[ame]http://www.youtube.com/watch?v=IWnYpulvSBI[/ame]
3. A lot of Hans Zimmer stuff
Hans Zimmer did the Sherlock Holmes soundtrack, but he has obvisouly done others - particularly some that work very well with games including soundtracks for...
- The Dark Knight
- The Last Samurai
- Gladiator
- Batman Begins
- The Da Vinci Code
- and more
Also, if you are looking for something creepy/eerie, check out the soundtrack for the Ring/The Ring 2 (also by Hans Zimmer)
4. Bill Brown - has done some amazing video game and film soundtracks, etc. Here's a sample of his...
[ame]http://www.youtube.com/watch?v=9OMf8Ny8xZQ[/ame]
Anyway, for those without paid accounts to get at music that easily, youtube is actually a really good resource. You can find a LOT of music there, including some of the ones mentioned by me here, and by others as well I'm sure.