I would guess that the core of the game development community is well represented on the two big sites, GameDev.net
. I think this here JavaGaming.org is the definitive Java-specific game development site.
Naturally, different technologies have their own homes, and small communities tend to grow all over the place. Dexterity Software
has a good set of interesting articles and a lively forum. I wouldn't say that OpenGL.org
has a community as such, but it has a useful set of forums
As for potential customers, the Association of Shareware Professionals
should be a good place for users to find software, but it's woefully under-advertised. The afore-mentioned Dexterity is a popular site, as are Download.com
and Real One Arcade
And many, many others...