Save yourself the hassle of tiresome file transfers from device to device and download the best cloud and sync app. Dropbox Mobile helps you keep your documents, photos and videos in one easily accessible place. You can also use pictures taken on your phone in reports or slideshows without having to email them to yourself first. First-time Dropbox users get 2GB of storage free, but you can add 500MB more for every friend you recommend. The app is now available for Windows Phone users, in addition to Android, iOS and BlackBerry devices.