Stumbled upon the google.loader object recently - lots of useful information that google pulls in for you without even having to ask. Specifically, I was trying to ascertain which city a visitor was coming from and display contact specific to that city.
Enter the google.loader.ClientLocation object.
No need for code snippets here of course, Google does a pretty good job already of documenting their codebase.
If you want to display geo-specific content, this is a good start. While it's client-side (so you'll have to be crafty in how you sanitize and implement it) and so not quite as robust as a server-side solution, hey, it's free and it works great for basic geoip functionality.
Mike