If you are Linux user you probably have heard about vim - text editor. You can use it to edit text file such as configuration files but you can set it up and use to develop web application for example in PHP, or create CSS style.
Andy Thornton Sr. Drupal Consultant (Security & Performance) gives approximately 30 minutes overview how he uses vim to develop for Drupal, lists plugins that make his work easier and explaines his workflow. Please visit this link to see presentation and slides.
I think I may try to use vim to develop web sites, but I need to learn how to configure it properly. I have been using this editor just for amending text file in text environment - but definitly it can do more much more that I use it for the time being.