I had a great experience being in a fraternity while in college (pledged Fall '98, graduated Summer '03).
In the beginning I was not out to anyone at all (had a girlfriend, etc), except for one brother who was openly gay. Eventually I found out that one of my pledge bro's was gay, so that was cool/comforting.
After a year or so, I slowly started telling a few people... some of my close friends in the group... None of them had any problems with it.
Then in 2001....
I decided to come out to the fraternity as a whole... and the brothers responded with support and encouragement (crap I was scared!!!!)
My fraternity bro's started calling me, emailing, etc... making sure I was okay, making sure no one in the group had issues, etc... it was GREAT!
Oh yeah... almost forgot... everyone except for one bro... my "lil bro". He totally flipped out... told me to F*** off, never talk to him again, how could I do this to him, etc.......
Well... I tried talking to him a few times over the next few days, but that did not accomplish anything. I was good friends with his girlfriend at the time, and great friends with his best friend from HS (who was also a bro)... between those two and a BUNCH of other fraternity brothers, he finally came around and decided to talk to me about everything instead of disowning his "big-bro".
After a week of him flipping out, and with the fraternity's support, things went back to normal between us. To this day (and this happened back in 2001) we are great friends! We joke about it every once in a while (well, he gets drunk and tells me how sorry he is for acting like a prick, etc.., and I give him a hard time, jokingly) and we have a drink to "brotherhood"!