"How'd you hear about us" box on registration page?
 

This is different from the "referrals" option where you say who referred you from the forums.

I'm looking for a mod or a hack that will be able to tell us where new members come from while they're registering...simply by quickly telling us in a little text box. Ideally, all it would be is just a one line text box with a one sentence title above it on the "/register.php?do=register" page that and then somehow sends the message the new user puts in to an email address or some sort of directory where we can look it the results.

Any ideas?