Box.net is not just a place to store files, but also a platform. Third-party providers offer their applications to Box.net users as "services" -- add-ins that give extra functionality. Each account comes automatically with Zoho and Picnik enabled. With Zoho, users can create documents and spreadsheets from inside their Box.net accounts.
It's not necessary to have the files created locally and then uploading, which is handy if a file needs to be created and shared immediately.
The following services are available through Box.net: Audodesk Freewheel, blog posting software, Echosign, eFax, Myxer, Picnik, Scribd, Snipshot, Thinkfree, Twitter, Zazzle and Zoho.