ValueClick, Burst Media, and Tribal Fusion are all CPM (cost per thousand impression) based ad networks.

However, that doesn't mean that you can just slap them up on your site and start rolling in the dough. It's just as important with CPM-based programs to perform well and keep a good CTR as with CPC-based programs.

A low CTR will mean that they will serve less impressions and at a lower CPM rate, or might even drop you altogether.