While this is not game related, it is vaguely game development related. As anybody reading this knows already, I am a supporter of open source software. Today I stumbled upon a really interesting blog post: http://whdb.com/2008/the-top-50-proprietary-programs-that-drive-you-crazy-and-their-open-source-alternatives/
This is an interesting link at it contains a list of 50 commercial applications with each commercial application followed by an open source alternative. Most of the open source alternatives were available for multiple platforms, including Windows.