Windows Live Quick Applications is a set of showcase applications put up by the Windows Live team to demonstrate how building a quick community portal around a theme is easy with the various Windows Live Services and SDKs.

Take a look at some of the sample applications put up:

Contoso University sample: http://contosouniversity.mslivelabs.com/

Contoso Bicycle Club sample: http://contosobicycleclub.mslivelabs.com/

Great use of Silverlight and various Windows Live SDKs to mashup applications.  For the complete source code and reference, you can visit the Windows Live Quick Applications project page at Codeplex: http://codeplex.com/WLQuickApps