CodySafe is a framework to help you create, customise and manage a portable working environment on any USB drive.
Install it on your USB drive (not your system drive) and, if you have autorun enabled, it'll launch automatically whenever your USB key is connected. Or you can always launch it manually by clicking StartCodySafe.exe.
Click the CodySafe icon in your system tray and you'll see the main launcher. This displays the contents of the USB key's Documents, Video, Music or Pictures folders at a click, and there's also an Explore button which opens Explorer at the key's root folder.
Click Options > Applications Manager, though, and life gets more interesting. Here you can "install" applications, which essentially means pointing CodySafe at the executable (which you should already have placed on the USB key). Your apps will then appear on the main launcher, making it look something like a mini Start menu.
And if you explore the Options dialog further you'll find other useful modules. You can set up scripts to run before or after launching a program, for instance (perhaps to help clean up if it's not too portable). While a built-in Drive Doctor can scan your USB to make sure it's healthy, probably something worth considering if you'll be using it to store important files.
There are also commercial versions of CodySafe available which add extra options. The Apps Depot helps you find and install portable apps, for instance; they can password-protect your drive, encrypt it, even remotely trigger its destruction if the key is lost. Prices start at $19.90.
We're not really sure they're worth the money, though, especially as the program doesn't seem to have been updated for some time. If you're interested in the idea, start with the free build: that'll give you more than enough to figure out CodySafe's usefulness.