Google Datacenter search compare tool
Google has a ton of data centers, and based on your luck and location, you get results from different datacenters. This tool hits 10 different datacenters and lets you compare the results.
One useful use of this tool is to do a site query. This will let you compare the number of pages that are indexed in google and see if you are on the way up or down.
example - site:www.attheboard.com