One of the very attractive features of .mac is the ability to sync multiple Macintosh computers; lots of the other .mac features are available for free through other service providers. Now you can sync multiple Macs with MySync according to this post on TUAW. Apparently you set up one Mac as the master and the rest of the Macs you want to sync as slaves. The best part is that MySync is free (note that Tiger is required).
I can’t wait to give this a try.