http://en.wikipedia.org/wiki/List_of_portable_software
http://www.makeuseof.com/tag/portable-software-usb/
http://lifehacker.com/tag/portable-applications/
http://www.getusb.info/55-portable-apps-for-making-a-usb-super-stick/
http://www.app-stick.com/products.php?cat=14
games
http://www.portablefreeware.com/
http://www.portablefreeware.com/resources.php
http://www.portablefreeware.com/all.php
http://flashdrivefreak.wordpress.com/
games too
http://www.softplatz.com/software/flash-games-and-more-free-games/
http://www.freegames4all.net/play-21930-2D_Memory.html
http://www.zoopgames.com/play-585-Memory-2000.html
http://www.1980-games.com/us/reflexion-games/memory-games/029.php
http://www.1980-games.com/us/reflexion-games/reflexion-games.php
* Just remember that some applications will tell you after a while that a newer version of the program is available and if you want to do an update. Press NO. You have to go back to the website where you got your application ( Firefox or Thunderbird ) and download from there the newer version and extract it to the same folder where your older application is.