Live HTML and CSS + livereload.js
Found this interesting video tutorial linked from nettuts. It's mostly CSS and HTML with a little javascript/jQuery. It's a good little exercise and pretty informative. It wasn't difficult to understand anything he was talking about. It has to do with creating an iframe to dynamic add CSS and HTML in the browser.
One thing that may be even more useful is to check out this livereload.js. It's a mac app. that automatically reloads everything you do with the CSS and HTML. So, you can have a window open with the page you're working on and another with a text editor and you don't have to keep moving around reloading the page to see the changes. Pretty cool!
Also worth noting the use of the HTML5 attribute contenteditable and the CSS webkit property box-sizing.