What kind of material do you mean? Philosophical treatments? First-person accounts? Anything good?
If they were really gay, they'd be Adam and Steven.
Sorry. Couldn't resist.
Try Jonathon Rauch's "Gay Marriage."
Andrew Sullivan wrote the book, "Perfectly Normal," before he turned all weird.
yeah, I've got Virtually Normal from the library. I hope it's good. Also, Orson Scott Card [sic] wrote an essay that's online...
I'll check out the Rauch. And the Sullivan anthology. Thanks.
For a relatively recent philosophical treatment, see e.g. Ralph Wedgwood, "The Fundamental Argument for Same-Sex Marriage", Journal of Political Philosophy 7 (1999), 225-242.