While it obviously cannot simulate the whole robot, I have had some success testing SmartDashboard extensions without a robot using the downloads from
http://firstforge.wpi.edu/sf/frs/do/...tables_2_0/frs.
Here is my netbeans project:
https://github.com/FRC-2429/FakeRobot.
SmartDashboardTest.java is just a copy of the SmartDashboard.java in wpilib with the initialization of the table delayed.
Linking "networktables-desktop-r208.jar" and "wpilib.jar" seems to make it work perfectly.