Thank you everyone for your recommendations. I loved Cooper's blog, by the way!
So, I finally found the information I was looking for. For future reference:
http://www.aphis.usda.gov/vs/sregs/ has links to all the state regulatory sites.
He'll need one for Alabama unless I'm exhibiting him (you'd think showing him off to my friends would be enough) but not one to get him back into Texas.
Guess I'll wait on that dog tote a little longer...