There are many tools available on the net to find out IP addresses of the users Think of something like finding who is the owner of a website, where the website is hosted, address and status of the Website. All this can be found out here in Who.is
This website is helpful for searching for a domain name to host your site and it also suggest other available domains for you.. and you can register there for your domain
Other Uses
You can also find the website is a real one or a phising site. This is mainly useful for the people who are doing the following
Online banking
Online Shopping
Making money transfer
etc
