RJ TextEd is a free Unicode text and source code editor with many useful development features.
The program has many powerful editing features. An advanced Search and Replace document includes support for regular expressions, for example; there's a built-in spell checker; tabs so you can have several files open at once; multiple (and more intelligent) clipboards speed up your cut and paste operations; and there are plenty of other additional features, everywhere you look.
In Notepad, say, you can only delete the current character. In RJ TextEd that are separate hotkeys to delete the current word, the previous word, and delete text to or from the beginning of the current line or sentence. As well as deleting the current sentence, all blank lines in the document, and more.
The program also includes many more developer-specific features: code completion, code folding, HTML validation, CSS/HTML preview, a syntax editor, colour picker, charmap and more.
And if you're thinking it sounds like you could develop an entire website in the program, you're right. And it doesn't stop there: RJ-TextEd also includes a dual-pane file manager, and you even get an integrated (S)FTP client to upload your files when you've finished.
Note this is the portable edition of RJ TextEd.