Dog's name & cell phone number. I think having your street address too is a good idea but we move a lot. Hopefully we will be settled soon. She also has her rabies tag and microchip tag on her collar.
I saw these tags on Etsy and I really like them:
http://www.etsy.com/listing/82069023...earch_type=all
http://www.etsy.com/listing/62171594...earch_type=all