CPM networks are at the heart of blog advertising. Matching the right ads to the right audience can result in high CPM rates and that means $$$. In some cases lots of it. Crenk.com has put together a list of the top CPM networks available to bloggers. Check them out-but remember to pick and chose carefully. The wrong ads or too many of them will turn off your readers and that's the last thing you want to do. Ads should compliment your blog and it's content!