Forums or discussion boards are a great way to encourage user generated content for a site or for companies to interact with their consumers. Many of the successful forums are standalone websites and not part of a larger organisations. Forums take time to administer and have costs associated with them. The costs to run a forum include the software platform that the site is run on and any updates; the cost of the hosting or the server and its maintenance; and other subscriptions costs to things like news sources and alerts to keep the forum topical. There is also the time cost for the administrator and moderators to run the forum and keep it clean and under control as well as initiate new discussion.
There are many ways a forum administrator can recoup this cost and even make some money by monetizing the forum. The easiest and most common way is to use Google’s Adsense. These do seem to do better in some niches than others. Another option is to carry eBay feeds of auctions that are of relevance to the theme of the forum. There are other affiliates that you can earn a commission or referral fee off for carrying the advertisement. Search for affiliates that have products that are relevant to the forums niche. Carrying advertisements for books from Amazon can be useful and so can starting threads to discuss a new book relevant to the niche can generate some sales. You can also direct sell advertisements, but need to be aware of the geographic region that potential advertiser are selling to. Some only target one country or region and most forums are global, so something like OpenX can be used to geotarget advertisements. The hardest way to make money from a forum is to have private password protected content that you charge for access to, but these will only work on a large successful forum where the public content is already good and the promise of even better content that is paid for.