Microsoft Live Mesh is the new hotness -- you can register your PC (and soon, your Windows Mobile device and even a Mac) with the network and then select whatever folders you'd like to sync. Cloud-based storage For The Win. It had been in preview mode, but now it's live (get it?) to anybody with a Live ID. Looks like the they'll start you with 5 gigs of storage synced across multiple PCs.
You can also share your Mesh-synced folders with others, post comments, and so on. You are almost surely going to want this -- check it at http://www.mesh.com
Can't wait for Windows Mobile support for this -- syncing files just by dragging to a folder on a PC (or even a Mac)? Sign me up.
Update: Whoops, maybe not. LiveSide notes that what's really happened here is they've simplified the signup process and lifted their cap for the # of users they'll allow in the Tech Preview. Best go sign up now, kiddos.