Versionate

Versionate will import and display your files right inside the browser, no desktop apps required. Supported formats: Word, Excel, PDF, OpenOffice, Powerpoint, and more. Versionate makes it really easy to share documents with others. It's like a wiki except it's awesome. Versionate does allow you to create free sites, with some limitations to the amount of storage you have for your content. Paid plans include options such as more storage space, SSL access, and permissions on documents.