ConTEXT is a powerful, free, and open-source text editor squarely aimed at programmers. Its feature set makes it especially useful for system administrators, toolsmiths, and Web mavens, all of whom often have to juggle many small files written in a variety of languages or markups.
The features which aid in this type of work (though ConTEXT is by no means limited just to this style of development) are the multitude of syntax highlighters (with the option to add your own), code templates (which allow you to insert preformatted snippets of code), the built-in file browser, and the ability to create projects which group files of different types, stored in different disk locations, together for easy manipulation and editing.
ConTEXT has the full suite of expected tools for text editing: fast file navigation, searching (including regular expression parsing and the ability to search multiple files and show all matches), word wrap/unwrap, ability to change line feeds between different formats, and so on. It has several code-aware features, such as the ability to comment or uncomment text according to the currently selected language. (It will use "/*" for Java, for example, and "&&" if you're editing Foxpro.)
It also has a few quirks. ConTEXT's built-in file browser, for example, sometimes does not display the directory tree as expected. I had a problem with "find next" that I was unable to replicate after noticing it (so it may have been user error). Both of these are related to an acknowledged issue with controls gaining focus properly, that is expected to be fixed in the next release (0.98.7).
As a free tool that comes with a boatload of editing features, ConTEXT is well worth checking out by anyone who regularly works with text files, especially those who work with code and markup files.