These two pages contain a lot of links to the microtonal community:

John Starrett's microtonal web site:
www.nmt.edu/~jstarret/microtone.html

Graham's microtonal web site:
www.microtonal.co.uk/

Email Lists:
The Tuning List
groups.yahoo.com/group/tuning/
This is one of the main lists for tuning. Theoretical discussion is the highlight of this list; still fairly avant garde related.

Make Micro Music:
groups.yahoo.com/group/makemicromusic/
This list is focused on making microtonal music. Things still "err" on the theoretical side here, but discussion definitely is more open than the main tuning list.

www.microtonal.org is the homepage for Make Micro Music.


Books:

The best introduction to the technical side of microtonal music I have found are the following books:

Nature of Music by Jon Catler
microtones.com/info_nature.htm

and

The Just Intonation Primer by David B. Doty
www.justintonation.net/primer1.html

Other books include:
Harmonic Experience by W. A. Mathieu

Please add your favorite resources

Note: I am really really really interested in seeing microtonal music expand to younger generations of composers and producers; especially electronic dance music. Microtonal music doesn't need to be viewed in an historical or explicit cultural context (IE eastern music, indian music, etc.).