Microsoft's free SkyDrive service is a part of the Windows Live offerings, and it's very similar to the Google Docs service. SkyDrive is designed to let you create and store Office documents easily, using the free Web Apps from Microsoft inside your browser. You can also store other files on the SkyDrive; you get 25GB of free online storage, with a 50MB per-file limit.
The default method to upload files to SkyDrive is via dragging-and-dropping into the web browser. You can also select and upload files individually via a traditional dialog box. Like Google Docs, SkyDrive doesn't offer integration with Windows. You use the SkyDrive website to access and upload files.
SkyDrive's sharing features let you share folders via web links that you either send to others manually or via SkyDrive. You can share with specific people, with your friends using Windows Live, or publicly with everyone. Sharing Office documents created using the free Web Apps lets you collaborate on creating documents among a group of people.