How do you manage your ad inventory?

I have some apps on social networks, and have to juggle between multiple networks. I've used Socialmedia, Tatto Media, AdSense, AdBrite and so on. These companies are supposed to solve the problem of putting the highest paying ads in your ad slots, but in reality the payout from the companies can be VASTLY different. How do you deal with this? Just bite the bullet and try every ad network out there, checking the stats every day to see which one seems to be the current best? I've seen some services that try to do this for you, but the ones I tried did not support the ad networks that I've personally found to be the best. I went from $5 CPM to 0.5$ CPM on a network today, so I'm left hoping that I would have had some automatic system to notice the change and immediately switch networks. I guess I could build my own screen scraping solution to check the eCPM every hour and switch, but is there some existing good solution out there?