Baking stone stinks
I admit it, I used my baking stone for frozen pizza a few times. Now there is some grease, cheese, ?? residue cooked into it. Every time I try to use it it smokes and smells like burning grease. Any ideas how to clean it? or just buy a new one?
This can happen with homemade pizzas too, no need to get a new one. Scrape off what you can with a spatula or bench scraper, soak up what oil you can with paper towels and then put it in the oven at 500 with the windows open and the fan on...it shouldn't take too long for it to "clean" itself.
I've left mine in the oven during a "self clean" cycle. It's not recommended by the manufacturer so your results may vary (i.e. it could crack, if there's moisture stuck in it), but it got mine nice and clean again.
And for some unsolicited advice... consider getting a Lodge cast-iron pizza pan for pizzas instead. Much easier to clean and won't soak up off flavors, heats up much faster, transfers the heat to the pizza faster, and more flexible (you can use it on the stovetop as a griddle, use it to roast vegetables, etc.). Since I got one, my pizza stone has been sitting unused on a shelf.
Most no-knead recipes specify that the bread should be baked in a dutch oven, in order to simulate the environment of a steam-injected oven -- so I'm not sure you need the stone for that either. Since I started using that method, I only use my stone for pizza and flatbread... And then, only in the winter, since I prefer pizza cooked on the grill :-)
Careful with leaving the stone in during a cleaning cycle:
I used to keep my stone on the "floor" of my oven, which worked great -- it got very hot, helped the oven maintain even heat, and never got in the way. I decided to run a self-cleaning cycle and left it in there, and was greeted with a nice clean stone. Alas, upon removing the stone I discovered that the bottom of the oven was badly damaged -- peeling/etc. Having a stone on the floor of the oven during cleaning was probably not something the oven manufacturer had ever tested for.
Since then I've kept the stone on the bottom rack. And my oven manual (a different oven than the one I damaged) clearly states that the racks are not to be left in the oven during a self-clean cycle, so I haven't had a chance to repeat the experiment.