Re:thinking is a directory of user-friendly free & open source software for the Windows (r) Operating System. For the most part, the focus will be on Free/Open Source Software (FOSS), but on occasion quality (spyware-free) closed source freeware will be included as well.
Now this one talks about open source applications for the Windows operating system. Am not very sure if the site contains only open source! But I did glance quite a few oof them. I also found some closed source applications mentioned there too. Anyways a handy place to search for some open source applications for windows.