Not everyone wants to lug a laptop around with them between classes or across town to a study session at the library. Or perhaps you're moving between a work computer, your home computer and a remote worksite computer, yet want to make sure you've got your suite of regular-use tools at hand ('cause you certainly can't guarantee they'll be installed on computers you don't control). This is where the concept of the 'portable application' comes to the rescue. Simply, a portable app is one that can run, stand alone, from a USB drive. Interesting concept made even more interesting with the development of application suites and websites like Portable Apps. If you need more detail, check out this extensive description of Portable Apps. The official line Now you can carry your favorite computer programs along with all of your bookmarks, settings, email and more with you. Use them on any Windows computer. All without leaving any personal data behind. The suite One of the neat things about the Portable Apps suite, is the ability to customize it to your specific needs. Once the Portable Apps application is installed on your USB drive, it's pretty simple to add or remove applications. If you check out the Portable Apps Suite, you get a bunch of common open-source applications to start with: Mozilla Firefox, Portable Edition (web browser) Mozilla Thunderbird, Portable Edition (email) Mozilla Sunbird, Portable Edition (calendar/tasks) ClamWin Portable (antivirus) Pidgin Portable (instant messaging) Sumatra PDF Portable (PDF reader KeePass Password Safe Portable (password manager) Sudoku Portable (game) Mines-Perfect Portable (game) CoolPlayer+ Portable (audio player) OpenOffice.org Portable* (office suite)     - Writer (word processor)     - Calc (spreadsheet)     - Impress (presentations)     - Base (database utility)     - Draw (drawing) The next level But if you want to extend the suite, there are more applications you can easily add, from system utilities, anti-virus and malware scanners, to media players, games and graphics editors. The Portable Apps suite is geared for Windows based computing, but you can find a list of portable apps for Mac over at FreeSMUG.