Updated: July 15th, 2006
Edit: updated link.
Rendr is a live CSS and HTML rendering tool. It displays what the page would look like as you type, making it great for rapid testing of page designs. Just paste some HTML and CSS and the page will change on the fly. The edit box is also movable and resizable.
In the meantime, if you found this article useful, feel free to buy me a cup of coffee below.