I LOVE the ProPhotogs.com forum! I'm on it at least once a day, more like 20-30 times a day! I joined about a year ago and it was well worth the money. I have learned SO much from the folks on this forum. Everyone is so open and honest about how their run their businesses and talk about their successes and sometimes failures.
I've been on other forums and well, some of them are just down right nasty. I can take constructive criticism with the best of them, but when people are just mean, why would I want to hang out with them? Not the case with ProPhotogs, yes, there is CC and Hard CC that is given out, but it's nothing mean and spiteful like other forums.
I have learned SO much from others just starting out and seasoned professionals. From lighting to equipment issues, folks sharing actions, textures and templates and other members post wonderful reviews of products they've used. The biggest thing I've taken away from this group is pricing. I didn't know how I should price myself, there are tons of posts on pricing including worksheets created by others to help you determine what you need to charge to examples of how others have priced themselves.
ProPhotogs is not just for beginers, there are a lot of seasoned pros on the site as well. I think with most forums, you get back what you put in. Ask questions, share results and when you ask for hard CC - know that you might not like what you hear, but others are trying to help you! Stop over and check them out!