mattb - 8:55 pm on Nov 3, 2007 (gmt 0)
I echo the use of Geoip from Maxmind. We block pricing and cart from countries outside the US and Canada. It works well and does not slow down the pages. A subscription to the country database is cheap around $100 per year. The db is downloaded and resides on your server for fastest results. You can also buy the city version but it's much more expensive.