Here's a good website for Reverse IP Address Lookups:
When you go to the site it displays your current IP address (external), which you can get the WHO IS information on, and it also displays a WHO IS search for other IP Addresses.
For the searches I performed I was shown specific IP information like country, region, zip code and an approximate geographic location (with a google map that was only somewhat accurate). Then you get the available WHO IS information about the IP Address providers.
It's a handy tool to have.