SailX is a free sailing environment where users race regattas virtually.
This environment was created several years ago by sailors for sailors. Mainly intended as a training tool for sailing rules and regatta tactics it soon developed into a full on-line environment and a game.
Sailing is free but if you register you will be able to name your boat, access more fields and use the protest system.
You can also buy a subscription, that will get you a ranking world-wide and access to exclusive events and more racing modes.