This makes me very happy: Dropbox is going to be integrated with Microsoft Office, across its desktop, mobile and online versions.
The Office desktop apps will be updated over the next few weeks to allow direct saving into a Dropbox account and the ability to share that file with others. The same feature will be added to the iOS and Android apps the next time they receive an update. Integration with Office Online is promised next year.
Office already has integration with Microsoft's own OneDrive service, but I've never found OneDrive to be reliable enough in syncing to use it as my main cloud storage option. Admittedly everything I create in Office already goes into a folder which is synced to Dropbox, but having one-click access will be handy if I'm using Office Online.