http://www.maxmind.com/app/geoip_country
I use that on every one of my sites to prioritise casino reviews, banners and links (and some text) by country. I try not to have totally seperate front pages as that could theoretically hurt SE rankings, but if you use it to target specific content, or like I do to just re-jig where info appears (ie: US visitors get US casinos at the top while UK get UK ones etc) it works well for conversions.
I also use it for navigation to show relevant pages by country. Plus it’s free 