Xinventions Forum. This is a pretty good forum, exept that you do not have to be registered here to post, and often, kewls come here and post a lot of crap. If you do not want to register your own account, than you can post here(I am registered here as NickSG).
Totse Forum. This is my favorite of all the forums I know about. Even though 99 percent of the rest of Totse is total crap, this is actually very good. You do have to registered here to post, and that is good so that no kewls can come here and post stuff. All the good stuff is in the Backyard Ballistics part. It is hard to get blocked from this forum, but you probably want to get to know a few people before you post a question that most everyone else might know about(I am also registered here as NickSG).
E&W Forum. This is a very good forum. I just joinged here less than a month ago. There are some very good topics around here, and if you do go here, dont post anything stupid, or you WILL get banned.