I don't know Leopard's slicker features well enough yet to spot the list of 40 that Gizmodo did, but this video is well worth a look anyway ... Here's some of Gizmodo's description:
I've got to say that this music video made using The Bird and the Bee's Again and Again is mesmerizing. Or at the very least, a really cool musical tour through 40 Mac OS X features and applications: it starts slow and boring with Word, but it ends being a complete explosion of synchronized eye candy using everything from Photo Booth to Stickies to Spotlight to Dashboard widgets to Stacks.