3. PushsharpA server-side library for sending Push Notifications to iOS (iPhone/iPad APNS), Android (C2DM and GCM - Google Cloud Message), Windows Phone, Windows 8, Amazon, Blackberry, and (soon) FirefoxOS devices!
5. Apns SharpApple Push Notification & Feedback Services Client C# Library
7. GCMSharpGoogle Cloud Messaging Client & Server Libraries ported to C#
9. EggsToGoXamarin Cross Platform mobile library for implementing Easter Eggs!
14. Android.Signature.ToolSimple GUI tool for Mac and Windows to help find the SHA1 and MD5 hashes of your Android keystore's and apk's
16. C2DM-SharpC# Client and Server Libraries for Android C2DM (Cloud 2 Device Messaging)