I used PayU2Blog and they are my favourite. I wrote a post on one of my blogs about 19 blog review networks: http://ineeddiscipline.com/2008/07/04/19-blog-review-networks/
i went with www.payperpost.com and made about... $30 so far?? or around there. they are pretty picky which I like. it takes awhile to get a good rep but when you do, the cash is okay. the advertisers rate your site and I don't think that you need PR to get accepted with PPP (tho mine do okay) I'll check this one out next. thanks
I am into SponsoredReviews and what is good about them is you do not have to tell your readers that it is a paid post, no banners below your post. They also have tons of advertisers to choose from. Your price can increase too.