FileSync
I’m including FileSync in this list even though it really wasn’t designed for .Mac use. FileSync is a freeware tool for synchronizing files and folders in two locations. It is incredibly easy to use and enables you to configure multiple reusable sync rules. FileSync’s easy-to-use interface enables you to use your .Mac account to sync files as easily as contacts and calendar information. You simply specify the folders and files that you want to sync; every time you connect to your iDisk, you can then sync all those files and folders with a single click. This can ensure that you always have up-to-date copies of your work, even if you don’t remember to copy every file to your iDisk after updating it.