Read original post by James Montemagno at MotzCod.es
At Build, Microsoft announced Shared Code Projects to simplify how developers are sharing code between platforms. We have had official portable class library support for Xamarin apps since late last year and it has been wonderful, however once you mix WP8 into the mix the PCL profiles get a bit limited. Shared Code Projects attempt to fix this by allowing you to create a project that are a shell for code that can be added into any project. It is basically glorified file linking with a nice UI to help you debug your code better per project. You will still have to do a bunch of #ifdefs though if you are trying to use functionality that is not available in a specific platform.