One of the fundamental decisions every person (read: geek ;) ) must make at some point in life is which operating system to use (and support until death). :) But there is a large number of operating systems that most people have never even heard of, and hence they cannot make a completely informed choice. :) Techradar recently featured a list of 10 less well known, open source operating systems.
The first entry on the list is ReactOS, originally created as an open source clone of Windows 95. Read more about it and the other 9 operating systems here.