Size and Weight:
If all you know about Velociraptor comes from the movie Jurassic Park, put those images out of your head right away: the villains in that blockbuster weren't really Velociraptors, but the larger (and more threatening-looking) Deinonychus. Velociraptors were vicious, all right, but they were also very small--and it's unlikely a 35-pound feathered raptor reminiscent of a giant chicken would have elicited all those "ooh"'s and "aah"'s at the local cineplex. (See 10 Facts About Velociraptor, a gallery of Velociraptor pictures, and a fossil history of Velociraptor.)
Jurassic Park aside, much of what makes Velociraptor so popular is the romantic story behind its discovery. The bones of this dinosaur were discovered in the remote Gobi Desert (on the outskirts of Mongolia) in 1922, in an adventure-filled expedition sponsored by the American Museum of Natural History in New York. Museum president Henry F. Osborn gave this raptor its name, Greek for "swift thief;" as a historical curiosity, he came within a Jurassic inch of choosing "Ovoraptor" (a couple of years later, he did bestow the similarly spelled Oviraptor on yet another feathered Mongolian dinosaur).
Velociraptor is one of the few theropods whose prey has been conclusively identified: paleontologists have found the fossilized remains of a Velociraptor locked in combat with a comparably sized Protoceratops, a pig-sized ceratopsian of late Cretaceous central Asia. (It seems that these two dinosaurs were fighting to the death when they were both buried by a sudden sandstorm.) See this article for an analysis of who would win an encounter between Protoceratops and Velociraptor.
Today, the main controversy about Velociraptor concerns what, exactly, this raptor looked like. This small theropod used to be depicted with boring, green reptilian skin, but lately the fashion has been to portray it with a coat of primitive, downy, brightly colored feathers, which has given artists plenty of leeway in their various depictions. Unfortunately, pending a spectacularly well-preserved fossil find, artists' conceptions will have to remain just that--conceptions.