rubber snakes on the ground....but you have to move them around the vegetable garden occasionally. Then there is the easier method, supply them with grain or bird seed for large wild birds, preferably in a location some distance from the veggies. They love that better than tomatoes.
You don't want to know my preferred method, but our squirrels aren't nearly so cute out here. Ours are the ground variety that don't live in trees, don't have cute bushy tails, etc.