Cook sausage in a skillet until browned and crumbly. Remove to paper towels to drain. Saute onion and celery in sausage drippings over medium heat until cooked through and softened, about 10 minutes.
Transfer sausage, onion and celery to a sprayed slow cooker. Add drained corn and tomatoes. Cut cream cheese into 8 cubes and scatter on top of vegetables. Top with grated white cheddar. Cover and cook 1 hour.
Stir to mix in cheeses. Add sour cream and remaining cup of cheddar. Stir again and recover. Dip should be hot and ready for serving after another hour. Dip will hold on low setting for quite a while. If your cooker has a warm setting you can turn it to warm.
Serve dip with scoop style corn chips and a large spoon so guests can put a big dollop on their plates
This makes an ample amount, approximately 8-10 cups. Refrigerate and reheat leftovers