Half of your homepage is adsense, thats a bit of an overkill, maybe you could use skyscrapers and place them in the sidebars. The rest of your forum and the content looks good, it's a good place to find info if you're into drumming. Why don't you use some eBay ads to sell drumkits and drum related articles on your site.
I noticed alot of activity on your forum. I would like to know the steps you took to cultivate that many users? As of how I feel about the site.. It seems a pretty basic straight-forward design. I agree that the google adsense are to big. At first I thought drumkit sales was the title image. I would change the locations because with the size the graphic it makes it look like the title and takes away from you and your site and what you are trying to do. I am assuming you are a drummer and wanted to bring like-minded individuals together. I have no problem with making some coin off of the venture but to me it screams sellout. You can always ask for donations from your users $1 or $2 dollars or whatever a piece to keep the site going... It would add up over time. The main thing you have to look at is that you are a forum it is more based on functionality and information then design. If you are still getting signups and your content is good, that is really what counts with your type of site.