WisMusic, now with Revenue Sharing!
If you have a Google Adsense Account, you can put your Publisher ID in your profile (don't worry, no one will see it but you) and earn a few clicks from other users!
Here's how it works: You start a new thread. Someone replies to it. Once there's at least one reply, a google adsense bar shows up after the first post and at the end of the thread. If you've put your Publisher ID in your profile, then a third of the time, your ads will show up on the page instead of our ads. Also, there's a twenty percent chance that the last person to reply will have their ads show up, if they've added their Publisher ID.
That means that you can make money by posting to these forums. However, if I start seeing a lot of fluff posts that are obviously meant to show your ads and not contribute to the site at all, I will not hesitate to delete threads and ultimately ban people for abusing the site. That said, I hope to see that this will motivate even more on-topic posting!
It's set up so you will never see your own ads, so you are protected from violating Google's terms of service forbidding clicking your own ads. Watch out if you're browsing the forums not logged in, though!
You can sign up for an adsense account through
http://www.google.com/adsense. To obtain your Publisher ID, log in to your account, go to "My Account". At the very bottom, it has the heading "Property Information". Under that are a few lines that might say things like "Adsense for Content". The Publisher ID number is the same across the board though. Take the part that starts with "pub" and all the way through the numbers, and paste that into your profile here (there's an example in your profile page).