This is just a variation of my UK Counties Select plug-in for ExpressionEngine which as you might expect, returns a list of US states in the drop down rather than UK counties. Usage of the plug-in is as follows:

{exp:np_us_states_select name="states"}

There are also some additional parameters you can pass that are detailed in the plug-in info page.

Download: pi.np_us_states_select.php.zip

Obviously let me know in the comments if you have any thoughts on how this can be improved. Enjoy!