What pupik and neon_duke said above basically sums up everything. Well said guys.
I have a Gay cousin, and a Gay Uncle. The Uncle was kind of a shock, since I used to hang around with him alot and he was like a best friend to me as a kid. But, I have a knack for judging character, and I knew in my head (and told my mother) that I think he was gay. With all that in mind, it was still a shock when he told my Grandmother (his mother) and my Mother (his sister).
Now, there is nothing wrong with Homosexuality, but it's still very unexpected and weird for you to experience, especially since you grew up together. The thing you have to get over during this whole thing, is that your friend does not want to be with you. He just wants your friendship, and as a good friend, he felt that you should know. Now, it took a while for me to get comfortable around my Uncle, but you have to try. The longer you act weird around him (even though you're still not comfortable), the harder it will be to act normal around him.
My advice? Go see him as often as you normally do. Push aside the fact that he's gay, and do everything you normally would do. Get his homosexuality out of your conscience and mind. Like Homer Simpson once said: "Don't let that little weener push you around!"