Ok everyone, "Me!" has withdrawn from the conversation. When I saw that the number of replies in this thread had ballooned from 10 to 40+, I got really excited because I thought I'd managed to spark excitement, interest and education. Imagine my disappointment when it turned out to be (almost) nothing but waring. For everyone left here who wants to just discuss dinosaurs, please stop replying to the irrelevant debate.
Now, I believe that someone a while back mentioned their surprise and curiosity about dinosaurs and feathers? Let me hand out a few cool factoids there.
First, yes, we now know that some dinosaurs had feathers. This trait was first heavily contested, because people didn't want to change their view of dinosaurs as looking like reptiles. Then, once it became more widely accepted, opinion started to swing wildly in the other direction. Suddenly people were putting feathers on all sorts of dinosaurs, usually in the wrong way. So let's go over a few famous cases.
We now know Velociraptor was entirely feathered. Specimens of this animal are found predominantly in China and Mongolia. Quill knobs can be found in bones all over their bodies. Quill Knobs are little holed knobs in the bones where ligaments that attach to feathers attach. However, velociraptor was in no way capable of a flight stroke, so it's entirely possible they were used for thermoregulation and not flight. At this time in earth's history, powered flight was exclusive to the Pterosaurs. Pterosaur wings are built very differently from the wings of modern birds and bats (the only extant animals to be capable of a Flight Stroke).
We also know that Tyrannosaurus Rex did not have feathers. This was one dinosaur that artists were quick to start re-imagining with feathers once the idea gained more acceptance, but that is not the case. However, a few specimens have been found with evidence of a partial feathered covering. There are two popular theories as to why. The first is that feathers were starting to emerge as an evolutionary trait at the eve of the destruction of the dinosaurs. This theory is weak, as it doesn't much more than speculation behind it. There is no evidence of an ecological or meteorological shift prior to the Cretaceous-Paleogene extinction event, so it's unlikely that T. Rex would have needed them. Also, unlike velociraptor, a much smaller theropod, Tyrannosaurus would have been capable of gigantothermy. This is a thermoregulation method somewhere in between ectothermy and endothermy (being cold-blooded or warm-blooded). As an animal gets larger, it's mass grows disproportionate to it's surface area. As a result, there is less surface to vent heat from, and more biomass committing cellular respiration and producing heat. If anything, thanks to its size, T. Rex would have needed help shedding heat, not keeping it (and feathers would not have been any real help here). The second theory is that they had feathers when they were young, and molted them prior to adolescence (or at least their first real growth spurt, around 3 years of age). it's very hard to find juvenile specimens. However if young rexes possessed feathers, they're more likely to have been short, soft, non-rigid downy feathers, and most likely have been a drab color. Just picture that, a cute li'l fluffy-baby T. Rex!
Also, theropods are the only group to have ever shown evidence of feathers. They do not appear in any other dinosaur species. It is largely believed that Theropods (bipedal, carnivorous dinosaurs) are the only saurian ancestors to modern birds.