This is the first time I've seen someone suggest split testing the ads that run on their own site. Are there any particular resources that you would recommend for this?
It's not too difficult. Suppose you have a 728x90 and 300x250 and want to see if a 160x600 would be better than the 300x250 unit. Create four new ads. 728x90 channel a1, 728x90 channel b1, 300x250 channel a2 and 160x600 channel b2. On your website half the time show a1, a2. Half b1, b2. Later go to AdSense and view stats by channel and see which made more.