I would like to write down Shruti music but I wasn't able to find notation software for that. Do you know any?
edit: Live Playback would be a great feature.
Here's a project to typeset Carnatic music based on LaTeX. Still in the development phase.
Check this out, it is interesting, http://vishwamohini.com/music/home.php . Useful for north Indian music notations & Tabla compositions. You can write, play & share notations & Tabla compositions. it is easy to use
Check out http://lilypond.org.
It has several options for microtonal music and is quite flexible and an extensive notation program.