Alternatives to AdMob

I have been using the AdMob extension by Milkman games with my ad based apps for about 3 years but recently AdMob rates have gotten really low and the fill rates are terrible compared to the previous 90%+ fill rate. So looking for ideas for an alternative extension that supports apps Air built via Flash and on a Windows machine. Anyone have good or bad experience to share?

Ill start with a bad. PlayPlace what a disaster that was, switched my apps to run their content and they went out of business 2 months later.