Windows only: If you're a big fan of portable applications, but there isn't a portable version of your favourite app out there, free app Cameyo will create one for you.
Cameyo is extremely simple to use. Just start it up, let it take a snapshot of your PC (which can take a little while, even if you don't have a ton of stuff loaded onto it) and install your program of choice. After you're done, Cameyo will take another snapshot and package that application into a portable EXE that you can take with you anywhere and run it normally (but without it affecting the rest of the system).
The really cool thing, as you can see in the video above, is that you can install pretty much anything — even add-ons to other programs, and they'll be included in the package. This means you can bring your favourite browser pre-bundled with, say, Flash and Java, among other things. Hit the link to try it out.
Cameyo is a free download for Windows only.