www.burstmedia.com has served me well for more than a year now, and I have pretty much given them all my ad-views to distribute. I have to say though, sometimes their number of default-views are a little high for my liking, but from what I've heard about other networks, all are pretty much the same.
Recently I have started using AdSense as well though, as it serves as a good "add-on" to BURST!, and it especially seems to be doing well for me below the content, compared to BURST!'s below-the-content ads at least.