If you're buying a convenient, uncomplicated, and stable synchronization tool, you could do much, much worse than Microsoft's SyncToy. Part of the Windows XP PowerToys add-ons, this tool makes it easy to keep folder contents identical on one machine or across a network. The first time it is run by you, SyncToy shall guide you through creating a pair of linked folders. passioninternet. Labeled as Left and Right, it will then ask you to pick from one of five synchronization methods. Echo works like a standard one-way sync, copying all files from Left to Right.
Synchronize is bidirectional; Contribute works like Echo but it won't delete files removed from the Left folder; Subscribe only updates files in common which have been updated; and Combine merges Synchronize and Contribute so that files are updated in both directions, but none are deleted. progsyourself here. SyncToy does support encrypted files. SyncToy also offers up a preview, stopping accidental loss of data.
However, the two feature omissions are hard to ignore: you can't synchronize across the Internet, and there's no scheduler. TuneUp Companion intros Mac beta. For the former, Microsoft does give you a different tool, FolderShare, but requiring users to manually sync all folders leaves SyncToy behind other free backup apps.