This is actually my answer to one of my friends who wonder, what is open source software.

An excellent Arabic white paper about open source software:
http://www.freesoft.jo/people/kefah/freesoftware_whitepaper_arabic.pdf

Wikipedia, have have a good article about open source software, look at:
http://en.wikipedia.org/wiki/Open_source_software

List of open source software for Windows:
http://ahm507.blogspot.com/2007/01/open-source-software-for-windows.html

List of open source software packages:
http://en.wikipedia.org/wiki/List_of_open_source_software_packages