<p>I'm writing an article about editing pages in order to hand pick what you really want to print. There are many tools (like "Print What you like") but I also found this script. Anyone knows anything about it? I haven't found any kind of documentation or references.</p>

<pre><code>javascript:document.body.contentEditable='true'; document.designMode='on'; void 0
</code></pre>

<p>Thanks!</p>

document.designMode is supported in IE 4+ (which started it apparently) and FireFox 1.3+.
You turn it on and you can edit the content right in the browser, it's pretty trippy.
I've never used it before but it sounds like it would be pretty perfect for hand picking printable information.
Edited to say:  It also appears to work in Google Chrome.  I've only tested it in Chrome and Firefox, as those are the browsers in which I have a javascript console, so I can't guarantee it works in Internet Explorer as I've never personally used it.  My understanding is that this was an IE-only property that the other browsers picked up and isn't currently in any standards, so I'd be surprised if Firefox and Chrome support it but IE stopped.