At the beginning of the year, Microsoft started a SQL Server 2008 Hero's contest, which was an open source contest to build a application leveraging SQL Server 2008 and one of the other newer technologies. The official rules were:
Ten finalists have been picked, and you can vote for the top 5 on the connect site.
I encourage people to check out all the projects and give them a whirl. There are a couple of really neat ones in there, and not just my own, I am having fun playing with a few of the others that were submitted.