- Should you use free software? - gives some helpful pros and cons, as well as suggesting a few good programs.
- Why carry a USB while traveling - software isn't discussed here a lot, but they do reference using 7zip.
- Why is portable software and why would you use it? - the above two make a strong case, but here's a more complete breakdown on all the reasons by someone who develops portable freeware (the maker of Snap2HTML)