my vote, aside from JGO
http://www.gamedev.net/reference/check the right side in "categories"
they have a lot of topics covering game design and programming. There is also some other parts of the website that's worth lurking around.
Is there any particular game mechanics or ideas you are looking for? You can often find pretty useful stuff just google it, occasionally trying it with keywords like tutorial or how. Id also recommend when searching for things like this, don't be language specific, as you can often get a decent idea how its done and just edit/rewrite it in Java.
