MediaMosa is open source software to build a Full Featured, Webservice Oriented Media Management and Distribution platform.

NicEdit is a Lightweight, Cross Platform, Inline Content Editor to allow easy editing of web site content on the fly in the browser.
NicEdit Javascript integrates into any site in seconds to make any element/div editable or convert standard textareas to rich text editing.

Symphony is an open source content management system designed to let developers program exclusively in the XSLT templating language.

The philosophy behind Symphony is that nothing should be sacrificed for flexibility – developers should have full control over their website’s markup, URLs and data structures.

CiviCRM is an open source and freely downloadable constituent relationship management solution. CiviCRM is web-based, open source, internationalized, and designed specifically to meet the needs of advocacy, non-profit and non-governmental groups. Integration with both Drupal and Joomla! content management systems gives you the tools to connect, communicate and activate your supporters and constituents.

Easy to use Wordpress plugin for accepting Paypal donations.

Best looking free open source CMS I've seen to date. The DNC used it to power the 2008 convention website. http://www.readwriteweb.com/archives/democratic_convention_web_site.php