Godspeed You! Black Emperor - truly wonderful Canadian collective
EnoWeb - dedicated to the work of Brian Eno
Spiro - ultra-refreshing serial-folk arrangements from Bristol
Morphogenesis - exploring the possibilities of live electronic music and collective improvisation
Vibracathedral Orchestra - "music that does not need much describing" (Julian Cope)
Stëllä Märïs Drönë Örchësträ - evolving electro-acoustic collective, purveying ambientkrautdoomragas to the discriminating psychonaut since 2003
Open Music Ensemble - creators of "authentic music", the performance arm of NYC's Open Music Circle
Ectogram - often portrayed as post-tonal dronedelic psych-pop noiseniks, they present you with art as a tool for evolution
S/T - undiscovered legends of the European lo-fi underground
 
Internet Audio Archive - a treasure drove of digital audio artefacts
open source record labels - Wikipedia explanation
Magnatune - They're a record label. But they're not evil.
          John Buckman's Magnatune Blog - from the project's originator
          Explanatory article "Magnatune, an Open Music Experiment" (from Linux Journal)
Loca Records - a similar sort of thing
Opsound - a "laboratory for new ways of releasing music"
minidisc.org - the MiniDisc community portal
 
Music Map - self-adapting music recommendation system
Audioscrobbler - a similar sort of thing
Last FM - best of the lot?
 
Resonance FM - freeform radio from London
WFMU - freeform radio from New York City
DFM RTV INT - has now absorbed Free Radio 100, Amsterdam
 
BioMusic: The Music of Nature and the Nature of Music
Music without Borders (Science News Online article)
 
Tribal Voices - music from UK's 1990's protest subculture
TreeWalk - Irish musical treeplanting project