If you are somehow related to working with computer one way or another, there is a real good chance that you own USB drive no matter what their size is. Most people just store some files on the USB drive and not being able to explore the full potential of it's use. Did you know that you can have portable application that you can run off from your USB drive which does not require installation to your desktop or laptop? Did you know you can have fully functional OS or browse the net or check your emails or have recovery application all stored in one USB drive (provided that it has enough memory size)?
If you are interested, pcstats have excellent Beginners Guides: Essential USB Memory Drive Projects & Tips.
Encryption, Firefox browser, word processing, arcade games and yes even an operating system can be run off your USB hard drive... if you know how! - Version 1.0.0
Also, lifehacker has her LH Top 10: USB thumb drive tricks.