Tim and the Tin Titan


DNS Toolbox
DNSstuff.com is a page that contains pretty much all the functions to get all the info that you would need on a particular domain name, including:
- Spam database lookup: See if a mail server is listed in 150+ spam databases
- DNS Timing: See how long your DNS servers take to respond
- Free E-mail Lookup: Is an E-mail address a known free one?
- URL deobfuscator: De-obfuscates confusing URLs.

Each function has a little help icon that tell you the correct usage. There is also a Canadian mirror (tiny bit faster for me).

They also have an Expert and Testbed page, although some of the functionality is repeated from the from page. The FAQ is here

It's a very useful page when you are setting up domains, making changes or doing test. And it's free, with not a single ad in sight.