A nice tweaking guide from the MaxPC folks:
19 Tips Every Windows 7 User Needs to Know - Page 1 | Maximum PC
I really liked the "Problem Step Recorder" (automatically records your keyboard, mouse, and other actions as screenshots and automatically adds comments. Wraps it all up in a hTML slideshow and zip file. Great for problem solving issues with people).
I also liked the guide showing how to load Windows 7 to a USB for installing, and a few other tricks, like the energy report.