Ability to add state fields for countries, which can be included as drop down options for "Users" details. It would also be useful to add it to the "shipping" module so you can create shipping rates for the states.
Important for ecommerce, and there needs to be a relationship with tax zones. In the UK the county (state) is not essential for a postal address but may be required by some payment gateway providers; maybe there could be an option to set this field to either be hidden / optional / mandatory. Also need to consider provinces eg Northern Ireland, Guernsey, Jersey.