While the Notepad tool bundled with Windows is fine for making quick text notes, for anything more than this it is somewhat lacking in features. There is always the option of using a word processor for creating more in depth documents, but sometimes a middle ground is needed - this is the gap that Notepad++ has been designed to fill.
The program has a small footprint and is quick to load, and while it has been designed as a replacement for Notepad, it has a great deal more to offer. The tabbed interface makes it possible to work with multiple documents simultaneously without the need to open several instances of the program and simple touches such as line numbering and syntax highlighting make it ideal for programmers editing code.
Notepad++ can be used to record and playback macros, and sections of large documents can be bookmarked for easy access. The program recognising a range of different coding styles, from C++ and Java to HTML and Perl and multiple documents can be viewed at the same time for the purposes of comparison, or a document can be cloned ready for editing while retaining the original version.
This is a hugely versatile tool which will prove incredibly useful for any coder, but also operates well as a more powerful text editor.
Note that this is the portable version of Notepad++.