Portable apps are lightweight and easy to use/install. You can download email, encryption software, photo shop type of programs, and media players ALL IN ONE BUNDLE, install to a USB thumb drive, and use them anywhere. It is great for moving from place to place with al lyour data. Plug in, get email, unplug and go to a new location. GREAT if you are using internet cafes or people's homes and need to stay on the move. They can be destroyed with a lighter quickly, crushed and ripped apart under your boot heel, or dropped into a sewer grate. Download the package here: PortableApps.com - Portable software for USB drives It includes everything you need, and is easy to run.
Truecrypt is highly recommended, and can be run directly from a USB key. TrueCrypt - Free Open-Source On-The-Fly Disk Encryption Software for Windows Vista/XP, Mac OS X and Linux