Bayimproviser
To my experience, about 80% of the experimental and/or improvised music events that happen in the San Francisco Bay Area get listed here. Also, browse around Bayimproviser to find out about other local unique musicians and venues that are friendly to unusual music.

Matt's Experimental Music Invite list
Sign up for this email list to find out about experimental music events and cd projects that are looking for odd and unique musicians to collaborate.
These opportunities are almost never for regular "gigs", but for ideas that will challenge adventurous folks to do stuff they're not used to.
These include but are not limited to: Moe!Kestra! (a guided improvisation noise orchestra), SoundShifts, Droneshifts, the Found Objects Festival, themed experimental music cd compilations, and remix projects. This is a moderated list. There are no announcements about non-participative shows, and no general discussion.

SF Sound Radio
A streaming radio station hosted by Matt Ingalls, featuring contemporary/avant-garde music mostly by local artists.

NoiseFX.com
Guitar effects pedals, samplers and other tabletop music equipment reviewed and sold from a noise musician's perspective.

Emusic.com
Similar to Itunes.com, except more geared towards "indie" music and muchbetter prices. (It amounts to $.25 per song or less.) My 2 newest CDs are here, as well as releases from Edgetone Records, Pax Recordings, and other interesting labels like Soleilmoon, Tzadik, Matador, Stones Throw, Kranky, etc.
 

Praemedia

Generally fun links