I’ve been using Dropbox, which lauched in September, to do secure file syncing between multiple computers, both Mac and PC (it also works with Linux). It’s by far the best hosted file synching solution that I’ve used so far. I also use it in combination with 1Password to securely sync passwords between my Macs. It works flawlessly.
Dropbox is also great for general file storage (it comes with 2GB for free or 50GB if you upgrade for $9.99/month) and to share your files with other people.