I have never done it but I do know that the industry use a process called Individually Quick Frozen, or IQF, when preparing frozen entrees and the such. Basically it boils down to freezing the individual components of a dish separately and then combining the ingredients together once they are all frozen, similar to the way gregkeller mentions.
This is why when you pull a frozen pizza out of the freezer you can still remove and replace the toppings. If you did not do this you would end up a pizza that resembled an ice disk. I have seen home-IQF done with Dry Ice, but that was only on small stuff like peas not a whole pizza.
If it was me I would probably form the dough, and stick it in the freezer to firm up a little bit, and then spread the sauce and add the cheese and then freeze it rock hard as fast as possible (we want to limit the number of ice crystals that are formed.) Then I would either spread the toppings on a cookie sheet and freeze them as fast as possible. As soon as everything is frozen solid, I would proportion the toppings and seal the whole thing in a zip-lock or foodsaver bag.
Now if you are just trying to save some time, rather than making something that you simply pop into the oven. I would recommend making up a big batch of dough, and then freezing individual dough disks. Then when you want to make a pizza, thaw the dough, spread the sauce, add the toppings and bake.
Hope that helps.