With the price of gas the way it is, one of the best ways to save money is to plan your errands. The best thing is to do as many as you can in one stretch, and plan the most effective route. That way you aren't driving to one side of town and back, or to home and back out several times.
So here is a handy website to plan your route.
Of course you can always use websites like google maps and add multiple stops as well.