Hmmm.... interesting one. If I had a time machine, could use it to go to anytime, but only once, and only for 24 hours and never again afterwards... hmmmm... I think I'd go forward a couple of thousand years and see if humanity has evolved in to anything like on sci-fi films - have we conquered space, got faster than light travel, inhabit other star systems, met up with any other "advanced & intelligent" species. It's only a shame I'd be hazarding a total guess on which point in time to check - too far forward you might find humanity has already been wiped out and it's plain emptiness, not far enough and we're still stuck on earth not doing much (which may always be the case!). It's just something I've always pondered - where is the human civilization going to be in the far flung future, if anywhere! I think 2,000 years would be a pretty good point to pick.
I'd like to collaborate with one of the future-lottery-winners though so I'll share my first hand experience, they share their winnings
2012 is the end...
But if you go forward in time that much, won't they have time machines? you might steal one, and keep going back and forward