Let people choose user group at registration?

[Jain Farstrider]

I'm preparing a board for Australians. Is there an addon that would let people pick a single usergroup from a list of usergroups when they are in the registration progress?

I would like to create 7 usergroups after the 7 captial cities of the states. That way when people register, they just click the apprioprate usergroup that relates to where they are from and they are registered into that specific usergroup.