The greatest source for music theory in the world.

http://xenharmonic.wikispaces.com 

http://xenharmonic.wikispaces.com/General+Theory

This was created some time ago now by Andrew Heathwaite and Jacob Barton, however many people have contributed to this encyclopedia of music-history, theory, math, philosophy, etc... One person whose efforts have been exhaustive and inspiring is Gene Ward Smith. Look at the updates on the wiki for a moment... o.O  

Some astonishingly clean pages have been created that sum up months of work of the Xenharmonic Alliance on facebook - thanks to Keenan Pepper and Mike Battaglia we have pages like:

http://xenharmonic.wikispaces.com/Mavila+Temperament+Modal+Harmony

These mavila modes in guitar scale-chart form can be found below in an earlier post. -RS