Oh man, I love google adsense. I remember the bad old days of awful flash and animated gif ads with awful pay rates. I'm constantly amazed at how much money my own site is able to take in from google, for such tasteful and restrained ads.
You guys might look into enabling image ads if you haven't already. They only show up if they'd pay better than the two text ads that would have otherwise been shown, and they're always static, small image files.