There are numerous excelent resources for game development on the web and in print. Here are some good starting points for web sites. Unfortunately the list is rather Linux centric. If you have a good resource for open source game development on other platforms, please email firstname.lastname@example.org.
Gamasutra is the online edition of Game Developers magazine. The site contains a large collection of articles from game developers and is highly recommended.
Linux Game Development Center
The LGDC has a lot of information about tools and development kits for Linux. They also feature news and articles about game development.
Linux Game Tome
The Linux Game Tome is a great place to find project ideas. Many of games indexed there include source code.