Sorry to revive a post so old, but I figured I'd add a small collaboration tool I just built. OP mentioned chat services and $LaTeX$. Check out http://texchat.juanbb.com/, a super-simple webchat that renders $LaTeX$ math (using MathJax). I built it to address guiding others through equations online (e.g. a tutor or studygroup setting), but it's as general as a chat can be. Cheers!