Even if you do most of your development work in an IDE, you're likely to need a good text editor for certain tasks.
If there is one topic that can get programmers into a debate, it is their personal choice of text editors! While most developers are now doing their work inside IDEs, there are still lots of ways to use text editors for development work. And for those who do not use IDEs, text editors are even more important. Here are five free or open source text editors that developers will want to check out.
Notepad++ is quite possibly the most popular open source text editor for Windows. It has a number of developer-friendly features, like syntax highlighted and regular expression search and replace. It recognizes all of the major programming languages out there and has a thriving ecosystem of plug-ins.
vi/Vim (Vim is a more advanced version of vi) is the most unique item here. It's been around for quite some time, and it's open source. What makes vi so interesting is that instead of the standard mode being "input text" with access to commands, the command mode is the normal state. Entering text is simply one of many commands. With its heavy emphasis on commands, vi has a steep learning curve -- but there's a big productivity payoff for those who are willing to learn it. Using vi is like using a *Nix shell in many ways. It's a small programming environment that lets you string commands together to accomplish lots of work easily.
If you ever want to see a fight between code-heads, ask a group of *Nix devs whether Emacs is better than vi. Emacs is the other big editor on *Nix platforms, but like vi, it is open source and available on Windows and other platforms, too. Emacs has grown to be almost an operating system unto itself, and it uses a Lisp interpreter to provide a macro environment. As a result, you see things like chess game plug-ins for Emacs. If you want a text editor with ultra-powerful customization capabilities, Emacs is where it's at.
4: NoteTab Light
NoteTab is my personal favorite text editor. It has most of the same features as Notepad++, but I feel that it is a more refined and better-documented product. The Standard and Pro editions are paid products (albeit very inexpensive, with free upgrades for life), but the Light version is freeware. With features like super-fast searching across directory structures and regular expression find/replace, NoteTab Light is definitely not lightweight on features.
SciTE is a handy open source text editor. It has the advantage of being a zero-install-needed application, and will run on both Windows and X-based desktop environments. It too supports all the usual code editing features, like syntax highlighting and regular expression find/replace. Like Notepad++, it is based on the Scintilla editor, so the two share a lot of capabilities.