Windows Live Sync (formerly FolderShare for Windows)
At a Glance
Want to synchronize your laptop with more than one other desktop or laptop--without spending a dime? Then give the free Windows Live Sync a try. With it, you'll be able to synch folders between as many computers as you want, and won't have to pay a penny for it. However, keep in mind is that it doesn't include online backup, as competitor SugarSync does. It only synchronizes folders from computer to computer.
It's even easier to use Windows Live Sync than it is to use SugarSync Free. The way you add and remove folders is simpler and more straightforward. You manage it all from a Web site, which means that you can set up your synchronization options in a single step, rather than multiple ones. Like SugarSync, it works with Macs as well as PCs. That said, I have been unable to get the software to work with the newest version of Mac OS X, Snow Leopard, so if you want to synchronize with a Mac running Snow Leopard, tread carefully.
Note: This link takes you to the vendor's site, where you can download the latest version of the software.