We also get all of ours from Boomerang tags. They're a bit more expensive than the machines, but very good service and exceptional quality. We get the rivet on style and rivet them to our dogs' leather collars. They look sharp, no annoying jingle and no chance of them getting caught on something and hanging up the dog or ripping off as with the dangly tags.
I ordered one for my brother from http://www.Cabelas.com It was 11.99 and really nice with the brass riveted plate. I didn't look at the prices at boomerang but the quality and shipping with Cabelas is excellent.
Also, check ebay (my answer for everything). We get our tags there, usually 2 for $4 or so. I just got Jedi new tags with her info printed on it, instead of stamped, since the stamping seems to get scratched up easy.