These are applications that
you can download on to a USB drive or memory card and use anywhere.
It's a way to have the software you like available wherever you
are. There's a large range available, including image editors, accessibility
tools, video viewers, DVD burners and more.
Illustrated on the right are some particularly useful: Chrome and
Firefox browsers, Komposer web design (similar to Dreamweaver and
FrontPage) and OpenOffice, the complete open source Office suite
with fully featured text processing, spreadsheets, presentation
and database apps.
The link goes to the PortableApps site from where you can easily
track down what you need.