The major constellations we recognize today mostly come from down to us from the Greeks. Who the Greeks took them from is anybody's guess, but there is evidence of the grouping of stars in some form of constellations from at least 5000 years ago, 2000 years before the Greeks. I would be willing to bet it has been going on for 10s of thousands of years, but I'm not aware of any direct evidence from that far back.
Despite my interest, I can only identify a few constellations; the Big Dipper (tail of the Big Bear) which I can use to find the North Star, Orion, and Cassiopeia (I just look for the "W", see picture below). I also can identify the Pleiades (pictured below) in a pinch.

So my question is, what is your favorite constellation that most people don't know but you yourself can find easily, and what is your trick for finding it?