A client turned me on to Live Mesh today - a Microsoft product which promises to "put you at the center of your digital world, seamlessly connecting you to the people, devices, programs, and information you care about—wherever you happen to be." Upshot: you add the devices you use (computers, mobile devices), add files, and then you can access those files from any of the devices.
It's designed for collaboration (you can share a folder with others, similar to MS Groove or to the now-defunct Tubes), and as with Windows Live Spaces, you'll see updates about what has recently changed within your mesh. Unlike Windows Live Spaces, you can't post a public file for consumption by anonymous end-users; it's an invite-only model.
It's still in Tech Preview, which means the feature set is not, ehm, complete:
Also, mobile devices can't be added yet. When they can, things should get interesting!