This is the issue faced by many people using more than one computer/devices.
Well, at the same time there are multiple services out there in the cloud that tries to solve this issue..
I have used following services which can solve this issue..
Dropbox and Live Mesh are still in private beta where you need an invite to join the service. Windows Live Foldershare is in beta but anybody having Live ID can join.
I am running out of Live Mesh invites right now, but I have few DropBox invites available.. If you want, leave a comment with your email id, will send one!