Portable Apps!
Have a disk on key? Have a computer that you can’t install an application on? Want to take applications with you? Portable applications may be the answer for you!
The people at http://portableapps.com have taken some essential utilities and made them portable. This means you can run them from a removable device (Like a disk on key) or on a system where you do not have permissions to run an installation.
There is also a cool portable launcher that can organize and launch you portable applications from one neat place. It is bundled in the Portable Apps Suite which gives all the tools most people would typically need in one place.
There are also portable versions of Firefox, Putty, and many more applications and utilities.