A portable app is a computer program that you can carry around with you on a portable device and use on any Windows computer.
Here are a few of the better known portable apps suites which you may want to check out!
PortableApps Suite is a complete collection of portable apps including a web browser, email client, office suite, calendar/scheduler, instant messaging client, antivirus, audio player, sudoku game, password manager, PDF reader, minesweeper clone, backup utility and integrated menu, all preconfigured to work portably. Just drop it on your portable device and you’re ready to go.
LiberKey currently includes 289 applications, all available in a few clicks! Areas covered: Audio, Video, Graphics, Internet, Games, Security, Education, System, etc.
Geek.Menu is a fork of the PortableApps.com menu system. It has many enhanced features such as support for truecrypt, categories, custom buttons, multi wallpaper switching, auto-executing apps on start, ejection scripts, special behavior for authorized PCs, local/www searchbar, etc.
PStart is a simple tray tool to start user defined applications. Designed to run portable applications (like portable Firefox & Thunderbird), you can start anything runnable from USB key devices or removable disks.
Lupo PenSuite is a free collection of portable software for everyone. It is completely free and portable and has been translated in 28 languages. There are over 180 programs and games included and more than 2000 programs and games available.
CodySafe is another software tool that turns any portable drive from a simple data carrier to a computer-on-stick. Carry your computer programs with you, manage them, launch them on any PC, and leave no footprint behind.
WinWenPack is another portable apps suite for Windows.
There are some more listed at The Geeks Club, including some for Linux users.
Know of any more? Do share!