A good ad network will give you a mixture of CPC and CPM ads. CPC ads pay when a visitor to your site clicks on a banner or text link through to an advertisers web site . CPM advertising is based on $X.XX per thousand views. Another variation is CPA - a visitor clicks a banner, passes through to the advertiser's web site and either purchases (a sale) or expresses interest (a lead) in the companies products or services. CPA pays the highest but usually has a much lower conversion ratio.
AdBrite also works like AdSense and is used by communities such as YoungEntrepreneur.com. As of May of this year, YE was making approximately $40 a day from the AdBrite ads, and the owner recently stated that the income has grown, though he did not say by how much. You may also wish to try banner ads, as they can produce good results. It all depends on your audience, though - perhaps create a poll at your forum stating that ads are going to be introduced, and then see what your users prefer: text, banner, or perhaps even something like inline text. This is what I would do.
Daniel B., CEO - Bezoka.com and Ungigs.com Hosting Solutions Optimized for: WordPress • Joomla • OpenCart • Moodle Data Centers in: Chicago (US), London (UK), Sydney (AU), Sofia (BG), Pori (FI) Email Daniel directly: ceo [at] bezoka.com
What's the url of your forum? Is it the celeb site?
AdSense can work very well for some sites and less well for others. It targets the actual words on a particular page, therefore showing mostly relevant ads with you then making money when people click the ads (CPC), but they also have some CPM campaigns as well so you are paid for each time someone sees an ad.
It looks like your forum is running vB for which there are some hacks to make better use of adsense, with ads appearing between posts in threads, therefore getting noticed more often and this generating more clicks.
Other ad networks can be better suited to other types of site as they will deliver a variety of CPM and CPC ads (which are graphical rather than text ads in adsense) and target only to categories - so your site would fall into a genral entertainment/celeb category.
Some networks aren't too keen on forums as generally they generate a lot of page views per user and the ads get lower ctrs (click through rates), and so will more often show CPC ads as then they only pay you when the ad is clicked rather than for each pageview.
I run a site about monetising your website in my sig if you want some information on any specific networks, or if you have any more questions I would be happy to answer them.