You have to verify links, no forum will tell you if he is nofollow or not ;) Just check the source code and if you find rel="nofollow" after links (in <a href> tags) it means that the forum is a no follow. Yes, they are not counted as backlinks and neither in link popularity counters. Many forums are dofollow, and making your link in your signature can make you earn many visits if it's a nofollow forum :)
well because a link is a link is a link. :) Link citations from relevant resources have better potential for driving qualified traffic to your website regardless of nofollow attributes.
I could not agree more!!! I think including some NoFollow link sources can bring in an incredible amount of traffic, especially if that site or forum itself has a lot of traffic. In addition it looks a lot more natural than just concentrating on DoFollow sites.