Turn your browser into a notepad with one line
Ah shoot. If Chrome allowed localStorage to be accessible from file:/// then we could add save (CTRL+S) and automatic load using this:    data:text/html,window.onload=function(){var a=document.body;a.innerText=localStorage.mydoc;a.addEventListener("keydown",function(b){b.ctrlKey&&83==b.which&&(localStorage.mydoc=a.innerHTML,b.preventDefault())},!1)};

Firefox will save it to localStorage but clear the local storage afterwards. Weird.Oh well.At least we can still turn our (Chrome) browsers into desktop calculators by pressing CTRL+SHIFT+J!(If you want the un-minified version of the code I wrote: http://jsfiddle.net/d5sGq/)