Many tech junkies are aware of TweakGuides, a quality website dedicated to the tweaking of games, software and hardware. Though its owner Koroush Ghazi has sadly since given up guides as such for PC games (console ports, exhaustive efforts, and all that), he has just released one for Windows 7, which should be great for anyone with the new OS.
The TweakGuides Tweaking Companion, as it is called, is written in plain language, intended to be understood by and useful for the most amateur to the most advanced computer users. It covers everything from new features to what all that craziness in your BIOS actually means, and offers a variety of guidelines for getting every bit of performance out of the OS and your games you can, given your needs.