I mostly muck around broadbandreports.com. It's another fairly techie site, with forums on just about everything you can think of.
I found this forum through a Google search after I finished OotP. I really liked it because it's not so huge that you get lost if you don't come and read all the messages once every half hour, but there are enough people to keep up lively discussions during the day.

Not to mention, a lot of other HP forums were shut down or closed to new members because of the new book. Now that's just ridiculous!
