Com Dot Game is a huge collection of online games that focus on both mainstream and gay productions. I recommend you search for 'yaoi' for a huge collection of gay games that go for the anime and hentai tangent. There are around 300 games in total that are available for you here including Ninja Yaoi, Pony Milking, Zebras In November and a wide array of other yaoi porn games. Note that searching for 'gay' here will yield pretty much the same results: they seem to love their yaoi!
The site is free to use and has the ability to show you recent submissions, popular options and featured games. I played a few and had a good time, although some of the gay Flash games here are very basic and one didn't even work for me. Still, if you look around, you'll find something worth your while: that's a promise!