Marc-Antoine Ross has knocked together a great little jQuery plugin, or extension if you will, which gives you a nice autocomplete country selector textbox (with little flags).
So in order for someone to provide you with their nationality, all they now need to do is start typing in a little form textbox provided and after two letters or so, they can simply select from the available drop down list the country which they wish to list.
The extension uses Jorn Zaefferer’s Autocomplete jQuery plugin, FamFamFam’s flag icon set and Aral Balkan’s ISO country data source in case you were wondering.
Related Link: http://www.devtaxi.com/tools/accountry/