Update: Foldershare is back up and running. As far as I can tell it was down for a solid eight hours plus...
I started using Foldershare a few weeks ago and really like it. It allows me to easily share files between my home and work PC's. 
Unfortunately I've started becoming reliant on the system.
Today I intentionally didn't worry about copying files to my iPod (to carry them to work) because I knew that I could use Foldershare to access my home PC from work. Dagnamit, wouldn't you know it; Foldershare has been down all day.
I still like the service but I hope there's not too many outtages!
As a final thought, I've gotta remember to make software that my users become reliant on. Not to intentionally lock them in but it indicates that you're providing an invaluable service. User reliance == success.
 It works by running a "satellite" app on both PC's. You can then access files on the PC (that the app is running on) through a web interface. So, from work, I can log in to the Foldershare website and view and copy files from my home PC. Sweet!