I'm in love with Vim with plugins, like zencoding and snipmate. I use it to write rst files (documentation), html, css, python, php, sql, and more importantly, version control with vcscommand.
And it's an editor available in all plataforms. You can develop software using Ubuntu, paying not a single cent in licenses. It's lightweight, so you don't need to have a powerful machine to be a developer.
You wouldn't believe how powerful it can become. BUT it's hard to start with, and messing up with it's configuration file (vimrc). Check github or other websites to look for pre-made vimrc files, already with a color scheme, with syntax indentation, and such.
Give it a try. Try to use gVim, it has a toolbar for beginners (but try to avoid it. After you start using only use your keyboard to develop you'll never come back to a mouse).