SailX Simulator is very cool...
Over the winter I tried SailX out several times, but I must admit my nerves were shot after a few minutes of racing against (better) sailors online. I spent most of my time sailing on courses that were not active so I could just see if I could make it around the buoys without tragic errors. Then, every once in a while, I would get up the nerve to jump on an active course and try to make some tactical moves as the 10 min. gun started me off on another palm-sweating race.
If you want to practice sailboat racing when not on the water - this is the place to do it. It will take some practice for sure, but once you get a handle on the key-strokes you need to tack and set and dowse the spinnaker you will be having fun... In two-dimensional views or three-dimensional, with zoom-in and zoom-out, there is a lot to do to keep you glued to the screen. The mark roundings will really keep you on your toes while you get to use real race rules in a virtual world - very much like real racing.
SailX Home Page
The Newbie page - A MUST READ :)
Sample video of how a race looks while you are in it: