Open source software (OSS) is computer software for which the human-readable source code is made available under a copyright license (or arrangement such as the public domain) that meets the Open Source Definition. This permits users to use, change, and improve the software, and to redistribute it in modified or unmodified form. It is often developed in a public, collaborative manner. Open source software is the most prominent example of open source development and often compared to user generated content. ~ Wikipedia
Usually free, open source software can be a quality alternative to custom designed websites. Highly and easily modified, these software packages are available for almost any need and their greatest feature are the legions of dedicated users who support 'their' favorite package in the forums. The level of support for open source is truly amazing to the un-initiated.
Perhaps the best known open source software program is the Internet Browser - Firefox. Be sure to visit the Open Source page for a chance to see some popular open source software in action.