internet.com's Linux/Open Source Channel 
A comprehensive channel for links to Web sites for open source developers and users, from the beginner to the seasoned expert.
Developer.com
Contains resources, tools, articles, discussion areas, and events of interest to Internet/intranet developers. Directories include: ActiveX, Java, JavaBeans, JavaScript, Microsoft and .NET, open source and VRML.
Open Source Defined
Do you want to get involved in the heated conversations around the water
cooler? At the very least, you need to understand the term Open Source and
what it means to the software industry. Here is where you start.
Suneido
Official Suneido Web site with FAQ, downloads, wiki, support, and more.
Webopedia's "Did You Know... All About Open Source"
Open source usually refers to a program in which the source code is available to the general public for use and/or modification from its original design free of charge. Open source code is typically created as a collaborative effort in which programmers improve upon the code and share the changes within the community.