Earn money for participating actively in forums. Interact with other members, reply to their discussions, and write good posts to earn money. Most of these forums share the revenue generated from the advertisements and the amount you earn largely depends upon how actively you participate. Some forums also pay per post, or per a certain number of posts made. The usual rate is 10 cents per post or more.
Most forums also let their user add their website link in their signatures. This helps webmasters get back links which in turn, helps in increasing the page rank and its overall search engine ranking of their website