USB memory sticks have replaced floppy disks as portable data storage devices but they have their limitations. U3 is a new version that takes the concept one step further.
U3 drives enable you to carry not only data but applications and personal settings, especially useful for Web browsing. You can plug one in to any PC, use it to access secure websites using your own user name, password, etc and at the end of the session simply unplug it and no trace of your activity is left behind on the host PC. It's ideal for use in Internet cafes and other public PCs.
They are not expensive either. Dabs.co.uk lists the Kingston 1GB U3 DataTraveller Smart USB2 at just 27.33 including VAT.
The U3 website has more details and a video demo.