Before I hauled my boyfriend home one fertile night, I was seriously looking for a donor. I was talking to one of my gay friends about it, but he wasn't sure, and had plans to keep asking around. Now, I've got this boyfriend on the other side of the ocean, and I'm 5 months pregnant. I must say, it's nice to have someone who's also involved with the pregnancy, who by some amazing chance also seems to be happy and excited about the coming baby, and just generally to share things with.
That said, we're not living together yet, and I have a sinking feeling that when we do I'll feel a little cramped for space, but after having nothing but space for most of my adult life, I figure it's worth the sacrifice. But I also would have been reasonably happy if I'd gotten one of my prospective sperm donors to do the deed.
Gay men are probably your best bet for sperm donation, in my experience.