At my company we use IP2Location (http://www.ip2location.com http://www.ip2location.com). They offer several databases with different data (from basic "IP-addre

At my company we use IP2Location (http://www.ip2location.com http://www.ip2location.com). They offer several databases with different data (from basic "IP-address to country" to quite comprehensive ones). You can get a DB as a CSV or binary file (in latter case the driver is required which also costs some money). The database is updated almost every month and you get free downloads. In my home project I wanted to save some money so just bought the CSV file, wrote a tool that converts it to a binary representation (~1GB) and a driver (.NET) that can find records very quickly.