nice site
Well your site is very nice, very well done layout. But its almost to good in the sense of adsense revenue.
I noticed this post over at the Adsense blog.
adsense.blogspot.com/2008/11/optimisation-essentials-part-i.html
Quote from article is below;
Publishers often ask us what the best ad sizes are to include in their site's design, and we always point them to these three:
300x250 medium rectangle
728x90 leaderboard
160x600 skyscraper
These ad units have proven in the past to deliver better results for both publishers and advertisers. Advertisers favour these formats, and if you've receiving all ad types, you'll find that advertisers will specifically target your sites more often. If you position your ad units well, users will be more likely to see these ad formats and find an ad that they're interested in.