What information can someone get from an IP address?
 

And how? Obviously the little bits of information from the IP address can lead to discovery of more information.

You can only get the ISP and a (very approximate) localisation if it's a private individual, but if it's a company you can sometimes know who it is and have its precise localisation.

In order to do so you must use a whois service (Arin for the US and Ripe for Europe: http://www.arin.net/whois/ , http://www.ripe.net/whois ).

Although not directly reachable from an IP address, if a site you are on logs you, it can also detect what operating system and web browser you're using etc.
The moral: use Firefox!