Massively scalable relational database using TABLE tags and jQuery
pivots.pivotallabs.com
pivots.pivotallabs.com
Just kidding, he did it cuz it's fun to write cutesy JavaScript hacks that leak memory like hell and turn any machine slower than a Core 2 Duo into a paperweight.
And if not, well he probably had a good time coding it.
But less ambitious: it's actually not a bad way (I think - I don't know enough about JQuery to have an idea about the performance of this) to do client side filtering of data presented in tables. His technique, at least, is more readable than the kludges I've come up with to do that.
In any case, this is fairly cool indeed.