gomezcoral.com is a good forum. I am an admin there. We don't have much members, but we are growing and have 6 or 7 really active members. It is salt, reef, and fresh water site. It's a really good forum, and has a nice layout. I also have a website aquatricks.com
One of the best sites that have helped me a lot with some problems i had is WetWebMedia (www.wetwebmedia.com).
If i am not mistaken, it is run by the well know marine biologist Dr Fenner. The incredible thing is that the support team answers your questions almost immediately. And their answers are always right and to the point.