Position the oven rack at the lowest level. If you have a pizza stone, place it in the oven on the rack. Preheat the oven to 425 degrees.
Heat the oil in a small saucepan and cook the green pepper and mushrooms over medium heat until crisp-tender, about 2 minutes. Cut the crusts into biscuit sized pieces using a biscuit cutter. Distribute the vegetables evenly over the crusts. Reserve 1 cup of the salsa and spoon the remaining salsa evenly over the pizzas. If you don't have a pizza stone, place the pizzas on a baking sheet. They won't be as crisp this way, but this is a lot less messy than placing them directly on the rack.
Bake the pizzas for 10 to 12 minutes in the preheated oven, then sprinkle with the cheese. Bake 7 minutes more. Serve the pizza slices topped with the reserved salsa, olives, cooked ham, shredded lettuce and sour cream.
Note: For variety, you can make a Greek style pizza, using olives, tapenade, spinach and feta cheese. An Italian style pizza uses tomato sauce and provolone cheese. A vegetarian style pizza simply omits the meat.