You'll be surprised, but Google Maps can be used for this purpose. For example, you can use your PC to navigate to Google Maps and then add different pins in different locations. The intelligent way of Maps will calculate the fastest route to that point. If you have GPS you can even synchronize your location with the route.
Also, you can install applications like TomTom GO Mobile or Sygic, add pit stops and then navigate using the phone's built-in GPS.