Video game music

Modules:

Amiga Music Preservation
This huge database lists authors and groups that made music on the Amiga. A good way to find modules if you know what you're looking for (search by artist, group or title).

Classic Game Soundtracks
Amiga modules.

ExoticA
More Amiga modules.

Atari SAP Music Archive
Atari modules (XL/XE).

High Voltage SID Collection
C64 modules (SID).

Zophar's Domain
Gameboy, Genesis, Master System, Nes, Supernes and Playstation modules (among others).

SNES Music
Supernes modules.

Nostalzik
Technical stuff about modules and players.

Midis files:

Video Game Music Archive
Midi songs, all platforms.

Mp3 files:

Amiga Music
Complete "albums" to download (Amiga games and demo tunes).

Amiga Museum
Amiga OST.

Amiga Remix
Amiga game remix.

OverClocked Remix
PC game remix.

OST Center
Thousands of music files from games, movies and anime series.

Kingdom Hearts Insider
Same kind. Games and animes.

Galbadia Hotel
Already huge and still growing site about video game and anime music. Also sheet music, midi files and more. I saw a console modules' section but it seems unavailable for now.

The Dark Side of Phobos
Doom's music remixed, I'm a fan!

SimCity.com Music Download
Jazzy music from Sim City 3000 (I recommend "South Bridge"!) and Sim City 4.

Spice Opera
Just for information. The composer Stéphane Picq released some time ago an album showing the musical themes of Dune. It is not distributed freely, but a version can be found on the p2p network.

On demand music:

Classic Game Tunes
Amiga game and Genesis music (among other) to listen to live.

News sites, blogs and webradios:

Soundtrack Central
OST reviews.

Muzax
Monthly French radio about retrogaming.

Game Playlist
Nice blog with video game music, old and new.

Kohina
"Kohina is a free "just for fun" web stream, streaming the classic 8/16 bit computer, arcade, and console music of our misspent youth, as well as the latest scene music from the platforms that remain active."