Wall art, graffiti art

Graffiti art, wall art, street art

Banksy, the Banksy website.

Blek le Rat. Artsy

Blek le Rrat’s website.

Graffiti Art. From Art Crimes.

Futura 2000

Intergraff
The international graffiti archive documents and showcases photos of graffiti from around the world.

New York graffiti.

Pure Graffiti

Wikipedia entry on Graffiti.

Wall art, a collection by Graham Reid.
Graffiti, street art, strange signs and murals collected by travel writer and music critic Graham Reid.

Berlin Wall. Art on the Berlin Wall
This collection of photographs documents the Berlin Wall and its art six months before its fall.

Banksy

Barcelona Street Art

Saatchi Gallery street art, a collection of photos and videos.

Streetart
A collaborative weblog for photos of DIY posters, guerrilla stickers and home-made stencils.

Street art
Wikipedia entry.

Street art websites.
The Open Directory Project