If you at least have one question answered yes, you probably will like portable applications. Portable Applications is just like another applications, except that they are... portable. It is designed to fit on your flash disk, iPod, external drive, or whatever. It involves no installation at all, no set-ups, no registry changes, and no whatsoever. Imagine all your favorite software in a single flash disk, you can pick any PC to work with, and still you have all the applications you need.
The applications are vary from Operating System to games, which virtually means that you have everything there. You can use Notepad++ for your editor, XAMPP for web developers, GIMP for image manipulation, FileZilla FTP Client, the amazing Mozilla Firefox, a complete OpenOffice suite, and many other things. You can check out the list of portable applications on wikipedia or on portable applications website, and yes, there's still a ton of applications that aren't on the list. You might want to check out the portable applications suite as well, a package that includes a set of commonly used applications.
Since Portable Applications are usually a modification from its conventional counterpart, it is only possible for applications in open source license. Commercial licenses in general won't permit any redistributions. Free applications with commercial license on the other hand permit redistributions, but not modifications. So most of the time you will find portable applications as a free, open source applications. Not bad at all.
Altough I'm not working with so many computers, I still found that portable applications are very useful. Its characteristics (not require any installation, leaving almost no "footprint") are remind me of a old-good days of the famous Disk Operating System (DOS). No installation required, and even if there is, most of the time it is just the same as copying a bunch of files to harddrive and that's all. Even uninstalling is just a simply files removal. No traces left. A clean and simple solution. Just love it.
Image taken from: http://portableapps.com/
Inspired by: http://brahmasta.net/2007/03/14/aplikasi-portabel/ (Indonesian)