OOdesk (pronounced as voo-desk) is a virtual desktop application offering free email, storage space, file sharing etc. OOdesk users can view and save documents, spreadsheets, presentations directly online without downloading. And this is done using Zoho's Remote API.
Once you are logged to your OOdesk account, you will be presented with a virtual desktop environment (a desktop-like feel within your browser window). Double click on My Documents and click on the Upload option. You can upload any file from your desktop into OOdesk. Shown below is a Microsot Excel file opened within OOdesk using Zoho Sheet's remote editor. You can view Microsoft Office or OpenOffice files, make changes and save them back to your OOdesk account.
If you are an ISV requiring such a functionality, do have a look at our APIs. We have a good many vendors who have successfully implemented our APIs (recently Central Desktop integrated Zoho Sheet). And it's not just for ISVs, any enterprise can make use of our APIs too.