I happened to stumble upon this site when looking for new background musics for my rpg sessions; it's really worth checking! I am now categorizing them where they fit best (scifi/space, fantasy or both (or something else)). For my purposes, it was searching music with 'epic' feel that gave me what I wanted. I'll still need to go through categories more, but so far every interesting piece has been in 'Epic' -category.
While these pieces are free, you can of course donate to the site if you like the music.
Now, why I started to look for music, I wanted to find a piece that would have Epic feel, and would feel more epic with every listening, but isn't something that everyone recognizes. I want to use that piece as a theme for a campaign I'm going to start, and perhaps another song for my current Beasts & Barbarians campaign too!
Now, I want to ask you if you have any special sources for music online? If you have, feel free to share them!