My dog wears an extremely light nylon collar, which is only used to hang his tags on. I never attach a leash to his collar, as he ALWAYS wears a Holt No-Tug Harness. I highly recommend the Holt Harness, particularly for dogs that pull. It totally changed my dog-walking experience. I kicked myself for not getting one sooner. I use it with a 30-ft retractable leash that allows Henry a great deal of freedom -- he hardly knows he's on a leash.

A picture of the Holt Harness and more information about it can be found here: http://www.petsmart.com/dog/shopping...oduct_31.shtml