IP Location Tools is a free web service that helps you detect the country/city of an IP address.

It can be used in 2 ways:

1. with API (no installs required)
2. by downloading the geolocation database

Although downloading the SQL database & running it on our own database servers is much more flexible, keep in mind that there are 1.4 million records in it.

The geolocation database is updated regularly (once a month). IP Location Tools offers another nice service: fraud detection. Again with an API request, with the zip code you submit, system compares the location of the IP and the area where zipcode belongs to. Can be very helpful, specially for e-commerce websites.