I find Wikipedia very useful, so for people who don't yet use or contribute to Wikipedia, here are some pages on free software that might be useful or that maybe you can improve:
First is the "free software front door" of English Wikipedia: http://en.wikipedia.org/wiki/Portal:Free_software
Articles with self-explanatory titles: http://en.wikipedia.org/wiki/Free_software http://en.wikipedia.org/wiki/Free_software_community http://en.wikipedia.org/wiki/Free_software_movement http://en.wikipedia.org/wiki/GNU_project
About the GNU OS: http://en.wikipedia.org/wiki/GNU
About the GNU+Linux OS: http://en.wikipedia.org/wiki/Linux
About GNU+Linux distros: http://en.wikipedia.org/wiki/Linux_distribution
About "open source", "FLOSS", "Software libre", etc: http://en.wikipedia.org/wiki/Alternative_terms_for_free_software
About free software licences, the different standards, etc: http://en.wikipedia.org/wiki/Free_software_license
And some detailed articles on people and organisations: http://en.wikipedia.org/wiki/Free_Software_Foundation_Europe http://en.wikipedia.org/wiki/Free_Software_Foundation http://en.wikipedia.org/wiki/Richard_Stallman http://en.wikipedia.org/wiki/Eben_Moglen
And there's too many more to mention, but here're a few more anyway: http://en.wikipedia.org/wiki/GNU_General_Public_License http://en.wikipedia.org/wiki/Copyleft http://en.wikipedia.org/wiki/GNU/Linux_naming_controversy http://en.wikipedia.org/wiki/Tivoization http://en.wikipedia.org/wiki/Software_patent http://en.wikipedia.org/wiki/Software_patents_under_the_European_Patent_Conv... http://en.wikipedia.org/wiki/Directive_on_the_patentability_of_computer-impl... http://en.wikipedia.org/wiki/Community_Patent
And most free software projects have an article about them too.
Free software portals for other languages also exist, such as: http://de.wikipedia.org/wiki/Portal:Freie_Software http://fr.wikipedia.org/wiki/Portail:Logiciels_libres