Maestro Mars Rover Viewer:
Requires Sun Java 2 (3D engine)
http://java.com/en/index.jsp
(click: Get it Now) if you do not have it.
Then surf to:
http://mars.telascience.org/home
Download Maestro and install.
Then check for update data and install: (ex: #1 Spirit Landing Site)
http://mars.telascience.org/update
Please do not confuse Maestro with DriveOnMars.com's drive on mars web-side java client.Surf the links; it will be pretty self explanatory, currently January 2004.