HoverPick is a small MooTools class that allows you to display a stylish menu-type picker... well it's kinda hard to explain but very easy to understand once you see it so, take a look at an example here: http://www.silverscripting.com/MooTimePick/hoverpick.time.html
It consists of 2 classes, HoverPick (the base class) and HoverPick.time (to pick time)... a 3rd class, HoverPick.date is in the work to (you guessed it) allow you to pick dates