Velociraptors were small feathered dinosaurs belonging to the family Dromaeosauridae of the suborder Theropoda, the same suborder from which birds evolved. They lived between 70 and 83 million years ago and were about the size of a large modern Thanksgiving turkey, something like 33 pounds, but a lot slimmer and well toned. The tail was rigid vertically, but flexible horizontally to aid in tight turns at high speed. While velociraptor did not fly, some of its direct ancestors possibly did - the evidence is scars on the arm bones for anchoring flight feathers. The wings did make velociraptor a fearsome predator, contributing to tight turns at high speed and the ability to run up steep slopes. Velociraptor drawing by Arthur Weasley distributed under Creative Commons Attribution v2.5
The velociraptors in the novel and movie "Jurassic Park" were clearly "conceptualized" for effect and do not resemble the real velociraptor in size nor did they have feathers - and real ones probably didn't hunt in packs. On the other hand, regardless of size, I don't think you'd want to meet up with a hungry one. We have good evidence those nasty hooks on the front of the feet were used to rip into the throats of victims - and they were very fast.
More on Birds.