If you frequently move and you don’t want to take your laptop with you all the time, or if you simply can’t use your computer, it’s really useful to bring with you a USB flash drive filled with your favourite/most useful programs.
A starting point to download free and already prepared apps is portableapps.com. They even have a custom menu to easily launch your programs and it’s ready to accept user-made apps.
There are tons of software ready to pack your programs in a sandbox to make them portable (cameyo.com, enigmaprotector.com, www.evalaze.de, spoon.net, vmware.com), so why would someone do this work by hand?