Ok, here's my entry to David Frum's parlor game to name 10 things from 1950 to 2000 that will still matter two hundred years hence (in no particular order):
1. The Apollo 11 moon landing (what we can do when we really try).
2. The fall of the Berlin Wall (the collapse of communism).
3. The PC/Internet/Mosaic and it's children (the real information revolution).
4. A child not yet 10 years old who will change the world in the next 50 years in ways that are impossible to imagine yet.
5. Global Positioning System technology (many variants already).
6. 9/11 and the aftermath (honestly, the fact that it will still be so prominent two hundred years hence is probably not a good thing).
7. Brown v. Board of Education (a lasting principle for the rest of the world as well).
8. The Super Bowl (it just gets bigger every year).
9. Rock & Roll (a broad category, but all encompassing from Elvis on)
10. The United Nations (Ok, I'm cheating by a few years here, and I won't say whether it is for good or ill). If you make me throw out the United Nations since it was founded in 1947, then I'll go with Monty Python's Flying Circus.
Original link from Tyler Cowen at The Volokh Conspiracy.
DOWNDATE: With just a little more thought, I think mapping the human genome probably belongs on this list. Monty Python seems more than a little frivolous when compared to this. But, for that matter, so does the UN.