The AFMM produces and commissions works which use pitches and musical scales which are not organized in the standard twelve tone to the octave equally tempered way. http://www.afmm.org/
Microtonal music page with large list of composers, mp3, WAV, MIDI, and Real Audio files of microtonal music. http://infohost.nmt.edu/~jstarret/microtone.html
Excellent discography of microtonal / xenharmonic / non-12 tone music (CD only). Contains addresses for record labels, and links to the artists (when available). http://www.xs4all.nl/~huygensf/doc/discs.html
Argues that the 34-tone equal-temperament scale is the most "natural" equal-temperament scale with fewer than 53 tones. http://m759.freeservers.com/natural.html