I myself am a bit surprised at some of the posts here. I am currently doing some contract work for someone who has what qualifies as a big board so I decided to swing in here for any ideas as far as optimization.
I run several small boards and they make more $$ in adsense than what most of you big boarders in here report. I have one board that probably gets 3-400 uniques a day and it averages about $4-5 a day alone.
I think one of the problems with Adsense is that people just throw it up there and expect it to work. You have to be creative and test your ad placements and layout constantly.
Use CHANNELS! Make sure your ads are relevant, if not, start using the adsense filter to get those out, and also read more about section targeting. Make sure advertisers know how to use adsense to place ads directly on your site.
I just find it funny that most of the time I am looking for more traffic, and yet here I come to a place where traffic is not an issue (in comparison) and yet obviously some of you are not doing the fundamental stuff right.
For those of you looking to perform better with your adsense, let me be the first to recommend this free forum which is practically the defacto standard in adsense conversation, and even has someone from the adsense team as a member:
http://www.webmasterworld.com/forum89/