IP Tools

Ensuring you have web site mark up that is valid and standards compliant is important for cross browser compatibility, accessibility and usability.

Ping Speed
Check to see if there is an active server or a domain name or not. Not very useful really, you could just go to the website and see if it is up or not.

Web IP Report
Lots of adverts, useful tool, horrible site.

Locate web IP addresses
Forget tracking spammers. Just accept it, they exist, what are you going to do anyway when you find one, even if you could, with this ridiculously simple tool (which is unlikely).

Browser Details
See what you browser registers as, plus all your computer details, internet connection etc etc. Very good and very interesting.

Server Status
A bit iffy in my opinion. Not certain how reliable the results are so don't worry about the slightly silly 'can't find email server' or 'can't find ftp server' warnings and error messages.

Web site speed test
Another web timer.