Adsdaq is all around a good CPM network. You set your own CPM price and a portion of your ads are filled depending on that price. For the inventory that isn't sold, you can use tags from other networks. It's a very innovative system. Here's my Adsdaq review.
There is no way that adsense pays better then adbrite cpm. CPC yes but not cpm. Tribal fusion, clicksor, cpx interactive, and many others are also good.