Sometimes you are given a machine where you don't have local admin rights. While it is understandable to lock down PCs to prevent viruses and licensing issues it can greatly hinder work. The PortableApps platform gives you the ability to run the applications that you need without installing anything or violating any license agreements. All the programs are free.
Here are some great free developer tools that run on the Portable Apps Platform
PicPick (This is like Snag It)
Zim Desktop Wiki
These are commercial programs that have Portable App Versions or can be run from the Portable Apps menu.