I recently wrote a series of short articles for LinuxInsider regarding IP issues as they arise in virtual worlds and video games. Each article was necessarily short, so there wasn't room to go into a lot of detail, but it provides some basic IP information regarding patents, copyrights, and trademarks for those that are interested:

The Rocky Legal Landscape of Virtual Worlds, Part 1: Trademarks (Nov. 12, 2008)
The Rocky Legal Landscape of Virtual Worlds, Part 2: Patents (Nov. 19, 2008)
The Rocky Legal Landscape of Virtual Worlds, Part 3: Copyrights (Nov. 26, 2008)