Music

Radio

Rainwave	Video game music radio. Has a request system if you sign in.
Datafruits	"Datafruits is a cooperatively owned and operated free-form net radio station." "Our station has little to no curation, and we believe that any song can be played." Has actual DJs if you catch a live show.

Streaming

Vidya Intarweb Playlist	Very old player of curated video game remixes and covers. It's been moved from flash to html5! An alternate player is available here.
8tracks	"Kip this is a dead link, what" 8tracks is to my knowledge the only website to ever be successfully bought up by users instead of going bankrupt. Your account is still there. I don't understand it either. (If you aren't familiar, 8tracks is a playlist-based streaming website, very popular for fanmixes.)

Downloads

Scoreworld	Instrumental music (OSTs and similar).
Doujinstyle	Doujin music (and games).
KH Insider	Completely normal Kingdom Hearts fansite. (Video game OSts)

Misc.

Rate Your Music

While rating and reviews are the primary purpose of this site, it's also an incredibly good catalog of music with accurate classifications. It also has an amazing recommendation system if you give it some ratings, but do note that ratings are public.