Discussion forums are one of the greatest things the internet has to offer as far as i'm concerned. Great sources of what is for the most part unbiased info. Used to be a big fan of boards.ie but don't use it all that often now. Its just not user friendly. Basic requirements for a good forum -the ability to search the archives with ease; ability to track ones own posts.
AAM would be the one I visit on a daily basis. As regards others, I would visit for specific interests as whatever your interests are, you can be sure theres a good forum(s) on the subject.