I'm in exactly the same position as you my friend. I run a small non profit site too, I have found Adsense has made me about $50 in the last couple of months, but I also offer advertising to my members and related companies. Recently, there is no demand - Myspace is killing off my site - but in the past selling ad space worked quite well. I just have the one ad at the top of my pages. I use
GAB - the best vB banner mod I have tried.