Here are some free extensions for your Joomla, if you are a publisher of course, provided by Joomla span
AdBrite Ad Extensions for Joomla! 1.0 and 1.5
Google AdSense Modules for Joomla! 1.0
Google AdSense Modules for Joomla! 1.5
Just visit:
http://www.joomlaspan.com/
