Comicster is a program you can use to catalog your collection of comics. I wrote it as a learning exercise when I first started developing in C# with the .NET framework.
Halfwit is a minimalist Twitter client, written in C# and WPF on the .NET Framework 4.
FunnelWeb is the ASP.NET MVC engine that runs this site. It straddles the gap between a blog and a wiki, and is targeted at real developers, lean and mean.