General:
CPU-Z
AnandTech CPU Cheatsheet
Anandtech Processor Cores Codename Cheatsheet
Intro to Processor Cache
THG Processors CPU Charts
TechARP CPU Comparison
AMD:
AMD Desktop Processor Quick Reference Guide
AMD CPU Chart
AMD Athlon XP Identifier
Calculate the p-rating of an AMD Athlon XP CPU
AMD A64 Product ID (OPN) Identifier
Intel:
Intel Processor Numbers
Intel Processor Spec Finder
Overclocking:
Lifehacker Beginner's Guide to Overclocking Your Intel Processor
SetFSB - CPU Overclocking software
TechReport Beginner's OC Guide
XbitLabs Newbie OC Guide
PcStats OC Beginners Guide
Hexus - Intel Core 2 Duo OC guide for beginners
THG OC Guide Part 1 Part 2 Part 3
AMD Athlon 64 General Overclocking Guide
Pentium 4 Northwood Overclocking Guide
Techware Labs OC guide
XbitLabs OC Guide
Overclocking on the 754/939 Platform - Short Media
Dual CPU, Dual Core, Hyperthreading:
2CPU.com
Dual Core Processing: Over-simplified, demystified and explained
XbitLabs - Dual Cores
Heatsinks and Cooling
Max CPU Temps - Heatsink Guide
Arctic Silver Instructions
Arctic Cooling
CoolerMaster
Noctua
SilenX
Speeze
Thermalright
Thermaltake
Vantec
Zalman
ZeroTherm
Water Cooling
Asetek
DangerDen
Innovatek
Swiftech
Here's the old sticky thread:
Useful tips about CPU's and Overclocking