You may want to give 7search.com a look see. They're a lower tiered ppc and have much lower bid prices. Lots of .05 and less clicks available. You do trade off the volume that google can provide, but in the ppc game, that may prove to be an advantage.

I've seen on some seo blogs that many big players are workiing the smaller ppc networks into their marketing mix to exploit the smaller competition. May be something to check out.