I've always said that xTube is a great destination to find amateur content and I will maintain that position for a very long time. See, unlike a lot of other tube site out there, this one has a great user community that means a hell of a lot of people want to share themselves getting down and dirty in front of a lens. To date, there are just shy of 80,000 clips in the gay amateur section. Quite impressive if you ask me!
Now like so many other gay sites out there on the Web, a big number of these just feature guys jizzing all over the places and recording themselves wanking off. If that's your cup of tea, well you're going to have a great time! Naturally, for others that might want something a little more substantive, searching for hardcore keywords is going to greatly benefit you.
For a more community-based amateur gay porn experience, be sure to check out xTube.