I've been using Foldershare for awhile now and I'm absolutely in love with it. Coupled with Exchange Server and an RSS aggregator in Outlook, it has pretty much solved the synchronization problems I've struggled with forever.
For those of you not familiar with Foldershare, it's a neat little service (recently purchased by Microsoft) that allows you to keep libraries of files synchronized across a number of computers via HTTPS (i.e., even behind corporate firewalls and public hotspots that otherwise restrict access). The software even provides web-based access to your files on any machine.
It's pretty amazing if you ever have to rebuild a computer - just install Foldershare, subscribe to the library, and you have all your files. I did this after running the recovery disk against my temporary replacement hard drive on my Toshiba, and it copied all of my 500+ MB of documents while I was in the shower.
In other words, Foldershare comes the closest I've seen to the utopia of virtual folders, where your files are just ubiquitously accessible.
A nice side effect of the system, though, is that it does a pretty good job of invisible, near-real-time backups . The loss of my tablet earlier this week is a prime example of why it's so effective here. \
Just minutes before the hard drive began to melt on my tablet, I was working on some stuff for school. I saved the file, checked my mail, and closed the lid putting it in standby mode. Then, screeching. Turn it off immediately, my neighbors said, or you'll lose all those files forever!
I shrugged it off, though, because I knew I wouldn't lose anything. Even that document I was working on 5 minutes earlier was already sitting safe and sound on my computer at home.
Think about that... my files were already backed up. The only thing I needed to do was make sure I was connected to the Internet (I am almost always connected, even without EVDO) and save the file.
Real-time, distributed mirroring.
For real redundancy, I can even throw this on, say, my parents PC and have my files backed up offsite as well. Or, perhaps one day I'll just be able to pay Microsoft for a similar backup service.
That's a pretty powerful thing. I'm already connected 98% of the time I'm using the tablet now, and the experience is only going to get better when things like EVDO, WiMax, EDGE, UMTS bring better coverage and faster speeds.