An interesting and enlightening article by Richard Stallman, Founder of GNU Project and Free Software Foundation

"When we call software “free,” we mean that it respects the users' essential freedoms: the freedom to run it, to study and change it, and to redistribute copies with or without changes. This is a matter of freedom, not price, so think of “free speech,” not “free beer.”

At GNU.org

The Free Software Directory
The Free Software Directory is a project of the Free Software Foundation (FSF) and United Nations Education, Scientific and Cultural Organization (UNESCO). It is a catalog of useful free software that runs under free operating systems — particularly the GNU operating system and its GNU/Linux variants. (Note: many programs run under other other O/S, also).
http://directory.fsf.org/