Now that I am studying for the PMP certification, I am working on understanding the difference between the Version 2 of the PMBOK and the Study Guide, which I used in 2003, and Version 3, which was adopted in 2007. In the process of examining this issue, I have found a number of web sites that look to be useful sources of information.

I.T. Toolbox Blogs - Project Management.
Herding Cats - a general project management blog.