WatchedIt is a project mainly written in JAVASCRIPT and C#, it's free.
Track What You've Watched
A web site built using MVC3 Boilerplate to track the TV shows you've watched. https://github.com/crdeutsch/MVC3-Boilerplate
Because my fiance keeps watching the series we like ahead of me so Boxee's "watched/unwatched" feature doesn't work for me.