The ability to program Android devices in C# using many of the libraries that you are already familiar with is rather cool. You may/not have heard about MonoDroid, which is an implementation of the Mono Framework, for Android. It has been in a closed beta. About 2 weeks ago, it became available in an open beta. While there are a number of things that it doesn't do at this point in time, you can tell that the Mono team is working towards getting many pieces working. If you are interested, check out the MonoDroid web site.