Preheat the oven to 350 degrees F. In a medium bowl, mix the mayonnaise, cream cheese, Cheddar cheese, Monterey Jack cheese, green onions and cayenne pepper. Transfer the mixture to a shallow baking dish, such as a 9-inch pie pan. Top the mixture with the cracker crumbs and bake until heated through, about 15 minutes. Remove the pan from the oven and top with the bacon. Serve immediately with corn chips, crackers or bagel chips.