Hey guys.
I've been working on an AdMob ANE for a couple weeks:
http://www.brinkbit.com/blog/ane-admob-android-ios/
I know there are already a number of these out there, but I couldn't find one with all the features that I wanted, so I decided to make my own. Mostly I was interested in exposing the AdMob SDK's new property "tag_for_child_directed_treatment" to make apps COPPA-compliant. I don't know if anyone else is really concerned about COPPA compliance, but it was something that my company has been paying close attention to.
The ANE also served as a great learning experience for me, as it was the first big Native Extension I've made. I plan on making a lot more of these in the near future, and it was useful to start with something that I knew was possible.
In making it, I realized there were a number of other aspects I could expose in the SDK that maybe some other developers overlooked, like the ability to preload both banner and interstitial ads. I tried to make it as full-featured as possible and I'm pretty proud of the result. This was mostly for my own benefit, but I'm hoping that other developers will find this useful. I spent a ton of time working of this and I didn't feel comfortable offering it 100% for free, especially since most of the other AdMob ANEs I found are paid, but I tried to make it as cheap as reasonably possible.
I am planning on making some free tools for Starling developers in the near future, so if paid stuff is not your cup of tea, I totally respect that and am gonna make stuff for you too 
Thanks for taking the time to read this.
Here's a tutorial I put together http://www.brinkbit.com/blog/admob-air-native-extension-tutorial/