Sell advertising - if you are running a forum with a lot of visitors but low adsense CTR then try selling the ad space. On my top forums I get approached regularly with people wanting to buy my adspace. So stick a for sale banner on your site
Great tip, especially since you can perhaps charge weekly/monthly rates depending on the CTR. Also, don't forget that you can include ads within your threads to encourage people to click on them even when reading random threads, mind you the CTR will be low if the ad isn't relevant to the thread.
