Many USB drives now come with the U3 technology. These drives come with a special flash drive controller and an application called Launchpad. Together these allow you to run software directly from the USB drive and when you remove the USB drive from the PC, no personal data is left behind. Unfortunately, U3 is a proprietary system so that you cannot install it on just any USB drive. Fortunately, the PortableApps Suite is an alternative that works in a similar fashion.
PortableApps.com provides a truly open platform that works with any hardware you like (USB flash drive, iPod, portable hard drive, etc). It’s open source built around an open format that any hardware vendor or software developer can use. The Standard Edition comes with ClamWin Portable anti-virus, Firefox – Portable Edition, Gaim Portable for IM, OpenOffice.org Portable, Mozilla Thunderbird and Sunbird (both Portable Edition) and Sudoku Portable. It runs comfortably on a 512MB drive. You can also download additional programs.
While not offering as many software options as U3, it is nonetheless a good (and free) alternative.