The announcement of the N8 brought a whole host of new hardware features to Nokia's Symbian devices. One of those features is USB On-The-Go. USB OTG allows users of the N8 to plug USB devices such as flash drives, external hard drives and card readers into their shiny new phone with the help of an adapter that comes with the sales package.
Nokia's user manual for the N8 (which can be found here) states that plugging in a mass storage device will automatically open the file manager and display said storage as mass memory, allowing the user to navigate through any files stored on it. External hard drives can be plugged in and accessed as long as they don't need more than 200mA of current (otherwise you can use an external power source).
With the N8's superlative camera, the ability to easily back up pictures and videos to external storage mediums could prove to be very handy. Perhaps USB OTG will also allow for USB keyboards and mice to be connected to the N8?
(Thanks to SaudiMac for the picture)