Microsoft released SkyDrive, an online storage service. You get 5GB for free! From now on you can access all your files and folders via the web browser. I really like it that I can use SkyDrive to share my files with others. For example that ZIP file with vacation photos.
Sign up is easy. It uses the Windows Live ID you've probably already have. I was up and running in 2 seconds because my PC has the Live ID Sign-in Assistent installed (comes with Live Messenger 8.5).
Now I'm looking for clients or integration in Windows Explorer. Till now I've only found SkyDriveViewer, an open source implementation on CodePlex. I tried this one out but I has a bad UI and didn't work at all.