The following are sites I use:

Craigslist

Yehey

Manila Bulletin

Microsoft

State of California

RichDad

www.zencart.com

www.ubuntu.com
www.joomlaresource.com
www.extensions.joomla.org
www.joomla.org
http://mambo.org
http://www.mambosolutions.com
http://phpnuke.org
www.maguma.com
www.freetds.org
http://drupal.org