If you want one of these too, check out the simple instructions at Abu Farhan's blog. Mine didn't show up at first, so I played around with my Settings. (Not sure what *fixed* it in the end. It might have been allowing "show link fields".) Also, it only shows up to 1000 posts (I changed the code to 2000, but it may not have altered anything--I'm not going to count.) And it doesn't show all the labels if you have a lot. Imperfect, but a nice start.
Other Table of Contents exist, but this was the only one that worked for me.