Knowing which country your visitors are from is important when you’re promoting affiliate marketing offers as some offers will only allow you to promote to certain countries. There are at least 3 solutions which I’ve came across.
GeoIP and GeoLiteCity are both free, contains free API samples and data in .dat, .sql and .csv format. Prosper202 can also be configured to use GeoIP. One of my favorite sites SourceForge.net is using them and I guess they are the biggest and most accurate player in providing geolocation information. No? Let me know.
Small, free, and easy to setup with only 2 tables.
If my memory serves me correctly, IP2Nation and IP2Country seems to be somehow related (one is the fork project of the other or something). It’s not free though and if I have to pay, I might as well go with Maxmind.