I like the small (non-animated) banner ads at boing boing. These are 150x60, but could be 120x90. While the site has a lot of them, I mostly ignore them consciously. However, sometimes one will catch my eye and I'll click on the ad. It's much more like reading a print magazine, and I don't have to look at a sea of text ads proclaiming all manner of mad things.

These mini-banners seem more laid back, and allow brand-recognition - which is a bonus for the advertiser. I'm actually surprised that Google has nothing like this. Adult sites *cough cough* have a lot of these and they seem rather *cough cough* effective.