What it is: More rules! In order for rye to be rye, it needs rye. Go figure. The mash has to be more than half composed of rye, in fact. Otherwise, it's a lot like a drier version of bourbon. Also, rye.
Where it comes from: Generally, Kentucky, since a lot of your favorite bourbon distillers also dabble in rye. They also, interestingly, make it at George Washington's crib, Mt. Vernon, presumably to dull the pain of chewing with wooden teeth.
Great examples: Jim Beam and Van Winkle Family Reserve.
Distinguishing qualities: Rye slaps bourbon's relative sweetness in the face, offering up a rougher, stick-in-your-throatier flavor that's a lot spicier. Also, you don't get much more distinguished than being made by George Washington.
Best cocktails: Classics like Sazeracs and Manhattans are completely transformed if you sub rye for bourbon.