IP and Domain Checks via a Chrome Extension

If you're using Google's Chrome web browser, you've probably noticed the extensions library that adds more functionality to your browsing experience.  If you work with computers or websites, a very nice extension can be found here:
https://chrome.google.com/webstore/detail/lhgkegeccnckoiliokondpaaalbhafoa?hl=en-US

It gives so much IP and Domain information and any valid DNS or IP address can be entered into it's search box.  Give it a try, it's awesome!

Mail Server Checks

While reading an article about troubleshooting an Exchange server, a person linked this website:
http://www.spam10.com/

It has some great utilities for not only email servers but all Internet-aimed servers.  It has DNS Lookup, a Blacklist checker, IP physical location finder, MX Record lookup for domains, Ping, Trace Route, Telnet replies, and more.  Check it out.