Pokemon Music
Yeah, OK, Technically this is video game music, but I felt it deserved it's own page, don't you? I tried to get everything, but if I missed anything important let me know. I will add FRLG and RSE, if they are ever needed (or donated.)

RBY (Red, Blue Yellow)
GSC (Gold, Silver Crystal)
Anime Music
DPP (Useful Bits)
PMD (Pokemon Mystery Dungeon)
Remixes
Other (TCG etc.)

The following contain every chirp, beat and tune from the NDS Games, HGSS In under 1MB, DPP is around 8MB, But BW is about 52MB.

HGSS (Heart Gold, Soul Silver)
DPP (Diamond, Pearl, Platinum)
BW (Black and White)

Finally, Is the best Pokemon Remix I have ever heard, Unfortunately, I don't think we will ever see this in a ROM as it is a MP3, But it still sounds pretty cool.

Pokemon Medley (7MB)