The USB mass storage device class is a set of computing communications protocols defined by the USB Implementers Forum that run on the Universal Serial Bus. The standard provides an interface to a variety of storage devices.
external magnetic hard drives
external optical drives, including CD and DVD reader and writer drives
portable flash memory devices, particularly keydrives
adapters bridging between standard flash memory cards and a USB connection
digital cameras
digital audio players (iPod, iAudio, Creative MuVo series and other DAPs)
high-end hardware media players
Card Readers
Portable Gaming systems (Nokia N-GAGE/Sony PSP)
personal data assistants and handheld computers
some newer mobile phones, such as the Sony Ericsson K800i