epochonaut

I'm designing an auction website and I want to have a drop-down list box that automatically populates with all the provinces/states/territories from a selected country. I also want to replicate an eBay feature that lets buyers type in their postal or zip code and search for sellers within a certain distance. Are there any public domain databases that I could download or any mash-ups I could use to help me do this? I'm hoping I won't have to collect this data manually...