If you haven't seen Ken Burns' ten-part series on 'Jazz' yet, then you owe it to yourself to track it down and watch. There are are excerpts all over YouTube, of course, but see if you can get hold if on DVD and watch it through your stereo.
In the meantime, here's the riveting intro to the whole thing that I love playing for friends, including Wynton Marsalis' electrifying summary of what jazz is about: "Jazz celebrates life, human life..."
If you've ever wondered what it takes to get the jazz bug to bite, then this is it. Click the pic to go to YouTube and watch and enjoy.