If you're looking to keep folders synchronized across different computers, Microsoft's FolderShare is a top-notch tool. But what about synchronizing local folders?
Microsoft's local sync tool, SyncToy, isn't bad. As part of the Windows XP PowerToys add-ons, it's convenient, uncomplicated, and stable. The five different types of synchronization might sound limiting, but they cover the gamut of sync combinations. Users can sync in one direction or bidirectionally. The other three sync types specify how the sync manages new, deleted, and updated files: updating only files in common that have changed, not deleting files from the source that have been deleted in the destination, and a combination of the two.
There's a glaring missing feature, though, that for my needs obviates the utility of any of those predefined synchronizations: there's no scheduler. More than anything, when I need folders synchronized--whether it's from my C: drive to an external backup or a thumbdrive I use to keep essential files and portable applications with me--I need a scheduler. Not being able to "set it and forget it" might not be a game-ender for some, but for me it's a must-have.
This is where SyncBack comes in. I use SyncBack as my backup utility, and I use it to regularly sync folders that contain files that are regularly edited. SyncBack comes with a set of predefined sync terms, but allows for a comprehensive selection of user-defined syncs that surpasses SyncToy's offerings.
You can customize SyncBack not just for file updates, deletions, or newly added files, but also adjust syncing behavior if the source or destination file has become larger or smaller than its match. You can even set SyncBack to prompt for user input, which sort of defeats the purpose of a scheduler except that you don't have to worry about accidentally copying over a file because of a rule.
The scheduler means, of course, that my fading and sieve-like memory is no longer required to make sure that I have backups and that I'm using the latest versions of files at home and work. The price of all the customization that has been rolled in to SyncBack is that the graphical user interface isn't very graphic. There's radio buttons and check boxes, and it makes a strong effort at being uncomplicated, but one of SyncToy's strengths is that the interface is heavily dependent on graphics. The interface window is wide, with big folder icons taking up a lot of screen real estate.
I've yet to come across a more flexible and forgiving freeware backup and sync tool than SyncBack, but if you use a better one, let us know in the comments below.