Tweakguides.com has released TweakGuides Tweaking Companion for Microsoft Windows Vista. The guide contains around 250 pages of tips and tweaks to customize and optimize every aspect of Windows Vista.

The guide is divided into the following categories:

Backup and Recovery
BIOS and Hardware management
Windows Installation
Boot configuration
Windows Activation
Windows Explorer
Windows Drivers
PC Security
Memory Optimization
Hard Drive Optimization
Control Panel
Services
Windows Registry
Windows Search
Internet Explorer
Graphics and Interface
Overclocking
Cleaning Windows and Maintainence

The guide is quite exhaustive and will probably take ages to go through it and implement the tweaks.

Download from here