I present mooShell – a tool which is helping with writing html, css and javascript. 
Just load the page, edit relevant fields and load the result into an iframe. It does allow to save results for further usage, like I did with this example: http://www.mooshell.net/wzRDj/. The tool is still in an early stage of development and definitely lacks some features. Plans are to implement logging, choice of javascript libraries (currently works with MooTools 1.2.3 only), and more.
