As the title suggests, what's your list of useful online webmaster tools (that Shaun didn't write Here's a few I like. Whois.sc Great for researching all the sites hosted on a server using Reverse IP or Yahoo/Dmoz listings for domains. Cost: email membership for limited options or $149/Year to display upto 1000 domain per server Reverse IP lookup. http://www.whois.sc/google.com Adsense Tracker Setup a few different styles of Adsense ads (contrasting / matching colour with your sites design or vertical tower / horizontal etc.), install the script (requires PHP / MySQL), setup a few ad profiles and see which performs best in real-time. Cost: free http://adsensetracker.info/ Wayback Machine Research archived versions of web pages. Cost: free http://www.archive.org/