Up until about a year ago the only real choice you had aside from using kiln wash when fusing, was Bullseye's shelf paper. It was ok in that it gave a nice smooth finish, but at around $5/sheet and only good for one time use it wasn't cheap. Spectrum then came out with their own version, Papyros paper, which costs about the same for the same size sheet (20.5" square) but with care can be reused several times making it substantially less expensive.
And cleanup is way too easy with the hazard of breathing in dust virtually eliminated. Here's a short video showing a Spectrum Papyros user with way too much time showing how easy it is to remove a full sheet with a spatula. She might be fixated a bit too much on the spatula thing but we thought the video showing how intact and unaffected the sheet was after a firing pretty impressive.