There are a few options - living in Australia it's a need to know.
Steroid cream is a great solution.
Alovera cream works too.
Anything with Euycalyptus in it
However (I don't know if you can get it in America)
CELESTONE - M OINTMENT.
It will KILL any sunburn over night. I've had burns that would have caused blisters stopped because of this stuff. It feels weird (doesn't rub in to skin - sits on top of it) and you wear it to bed, but my god it works a treat. In a country with Skin cancer rates through the roof this stuff is amazing!
That being said my Dad's a doctor so it's probably prescription.