I received a email the other day with a list of sites that I thought where great and I wanted to share with everyone. Most of these I have read about or used at some point along the way, but a few I haven't. Disclaimer: I in no way claim this is my list. Hope everyone finds it useful, I know I did. 1. SEMRush.com ? Lets you find out what keywords your site is ranking for or even your competition's, even find out ppc keywords they are paying for. 2. Copernic Tracker ? Track changes made on your competition's websites. 3. WhatWPThemeIsThat.com ? The name says it all! 4. WhoIsHostingthis.com ? The name says it all! 5. WayBack Machine ? web.archive.org - See what a site looked like in the past. 6. DomainTools.com ? Need to contact a site owner, this tool can help. 9. BuiltWith.com ? Want to know a websites technical info? Here is a partial list of things you can find out. Server Information Google Webmaster Usage Statistics Site registered at MSN/Bing Webmaster Hosting Provider ServerBeach Nameserver Provider Email Service Provider Content Management Systems Frameworks (e.g., PHP Usage Statistics) Advertising/AD networks Analytics and Tracking There are many more I won't list here.