Notepad++ Portable is the handy Notepad++ text editor packaged as a portable app so you can do your development on the go.
It has all the same great features of Notepad++ including support for multiple languages and an extensive plugin system, but there's nothing to install.
Notepad ++ can be found here on the Portable Apps site.
Details of how to use it can be found at the about Notepad ++ site