After my last post I poked around on LoveYourPets.com and found out that they now do dog tags (military style) and other ID and utility tags besides pet tags, so they're an even better choice. Also the dog tags are engraved stainless steel rather than the stamped thin sheet that some of the other places sell so they're probably exactly or almost exactly what Road ID sells for dog tag style ID anyway.
At $3.50 for engraved stainless it's hard to beat.