If you have not already, I would recommend checking out Campus Pride:
http://www.campuspride.org/
Unfortunately, right now it appear the website for Lambda 10, the area of their organization that specifically focuses on LGBT issues in the Greek system is not working, but this will give you an idea of what that is:
http://www.campuspride.org/gaygreek.asp Shane Windmeyer, the founder/director of Campus Pride, is very knowledgeable on this subject.
Good luck!