Kansas State Anthropologist Michael Wesch has put together a brilliant brief animation on Web 2.0 ... The Machine is Us/ing Us, part of KSU's Digital Ethnography project.
Exceptional work, truly worth five minutes of your time.
Thanks to John Battelle for the link.
Those interested in learning more about Web 2.0 should also read this essay by Danah Boyd: "Why Web 2.0 Matters: Preparing for Glocalization"
2/19 follow up: Batelle's interview with Michael Wesch (also look for Wesch's input in the comments).