Here is the link Nicole- http://www.dogchannel.com/sidebar/sidebarmicrochip.aspx .
Sorry it took so long, but sunday is football day with the Vikings.. lol.
All of my dogs have been microchipped since it was available to us. Even my little rescue had a chip. The purpose of it is to not only insure ownership, but more so to get the dog home. Any vet- when a client brings in a new dog around here, will scan the dog for a chip. If avid sent out an alert on a possible stolen or lost dog, they have to contact AVID.
I am not sure if there are other chip registration companies, as I always used AVID. YOu can also, at any given time update the information with phones numbers, address etc. Or even a medical alert like if a dog becomes a diabetic etc. Also- because I always had multiple dogs, I use the group rate and not a single. Also when I have puppies I supple the owners with a microchip to give to their vet to put in the dog when the puppy is old enough. Large dogs you usually have to wait until the growth spurt slows down.
Oh- and everytime you go to the vet afterwards for wellness exams etc., have them scan the chip ( will cost you nothing) to make sure its easily read.
With mine I have a key ring on my keys with their numbers listed in a brass plate. If you do loose a dog, call not only avid, but the local shelters and local vets. And include the dog is microchipped on your posters you put up.
Hope all this helps.