Free forum without Ads?
 

http://support.forumgogo.com More powerful than the phpbb
This is a great site that is completely free, and can make some cool
forums, here's an example of one, you can make your own topic, polls,
and replies etc, and you can have an accout for every member. This
next link is an example of a forum made from invisionfree.
http://support.forumgogo.com