Useful Internet Tools:
DNS Watch
CentralOps.net
DNS Stuff
Trace, Lookup, Ping
Internet Connection Speedometer
Test Download Speed
Web Page Analyzer
What Is My IP?
Built With
Website Speed Test
Dig Web Interface
Global DNS Propagation Checker
GeoPeeker - See how a site appears to the rest of the world
IP Calculator / IP Subnetting
IP Subnet Calculator
Security Tools:
Panda Security ActiveScan
Trend Micro Clean Up
McAfee Virus Scan
F-Secure Online Scanner
useit.com: Jakob Nielsen's Website
Contrast Ratio
Check Colors
Color Contrast
Tavern Puzzle