Open Source Initiative (OSI) at http://www.opensource.org/
Developer.com at http://www.developer.com/open/
Open Source Technology Group at http://www.ostg.com/
GNU Project License List at http://www.gnu.org/licenses/license-list.html
Freshmeat at http://www.freshmeat.net
SourceForge at http://www.sourceforge.net
Why Open Source Software/Free Software (OSS/FS)? Look at the Numbers! at http://www.dwheeler.com/oss_fs_why.html