DropSync is a wonderful app which allows syncing of data from your Android device into a folder on your Dropbox account. The application is completely free and once set up works entirely in the background just popping in the notification tray.
The app can even run at a real-time sync if preset conditions such as WiFi and battery level are met. I even use it here at Land Of Droid in order to get screen-shots onto my computer, as it’s all wireless and automatic. You can use it for anything, be it those important documents or just your Instagram photos. Plus, the app appears very stable and if you have the official app installed you don’t even need to re-login.
If you wish to support the author and upload files over 5mb, go pro: