A recent update to the Xbox 360 firmware now enables the console to use USB flash drives as a method of storage.
A minimum of 1GB of storage must be available on the USB flash drive for it to function properly. A flash drive with a capacity of up to 16GB will be supported; however two may be used simultaneously for up to 32GB of storage. Anything higher than a 16GB capacity will only have that amount recognized, while all other space is simply ignored.
Visit www.xbox.com/en-US/storage/default.htm for more information.