Depends how big you are. Sometimes if your a bigger community (around 500+ members) you can sell t-shirts on cafepress, and stuff like that. Make a little cash like that, expecially if your a good designer. You can also do adsense, but thats not good if you don't really want adverts all on your website. Sometimes you can sell advert space to your memebrs on your board. That sometimes even works. It really does depend on how many members you have, what your willing to do, how good your graphics skills are, and how many members you have. Also sometimes it helps to have a better topic, like lets say gamming, more people are into gamming then maybe into school. If you get that.

You can make money with adsense but I suggest you promote your website well to increase your traffic.Traffic is the source of earning.