(ATTN: alistato) On Microtonality: I'm not aware of any grand theory of microtonality, or even a common language; rather, a there are a variety of techniques for making use of it.
In the context of Western Art Music (i.e., Classical music), there are a number of music theory journals that publish articles on microtonality. Perspectives of New Music recently published an article I found interesting, "The Microtonal String Orchestra", by Dylan Crismani. The article discusses a method for tuning an orchestra for microtonal music as well as a method for tuning a piano to facilitate composing for such an orgestra.
Perspectives of New Music has a long history of publishing on microtonality. In 1991 (volume 29, nos. 1 and 2), they published a "Forum" on microtonality that is considered something of a landmark. Other journals include Journal of Music Theory and Music Theory Spectrum. And these journals will also suggest particular authors to search for. Robert Hasegawa, for example, is a name that pops up frequently.
Outside of Western music, there are a large variety of "microtonal" tuning systems used in various music cultures around the world. Studies on these could be found in ethnomusicology journals or journals devoted to particular cultures.
