Nytimes-style popup when the user makes a selection
<p>When you select text in an article on nytimes.com this little ? pops up at the end your selection:</p>

<p><img src="http://img193.imageshack.us/img193/1316/827200941520pm.png" alt="alt text" /></p>

<p>What's the best way to implement something like this on my site? Are there any pre-rolled libraries for doing this?</p>
