Great thread Cris
Assuming I would be safe and able to skip through time to observe only, and not affect anything, these are the places and times I'd like to go to.
Watching how the pyramids were made. Finding out how those lines in the ground (I think at Nazca?) that from the air are drawings of spiders and birds etc., I'd like to find the answers to all the questions in Chariots of the Gods, like how those gigantic statues on Easter Island came to be.
I'd like to witness the formation of a crop circle, (these days they're getting more and more elaborate). I'd want to skip through time and watch the evolution of man. I'd like to watch things that were happening in the time of Jesus, what he was all about and how the bible came to be written. I'd like to have a look at the dinasaurs and watch how the continents formed, dividing up the land and producing different animals on different continents. I would like to have gone to the moon with the astronauts; a view of the stars from space would be amazing, so would looking down and seeing our own planet.
If I could interact without causing any damage I'd love to talk to Nostradamus to try to compare what he was 'seeing' to history up to the present time. I'd have loved to talk to Carl Sagan.
Lastly, for now, because it's 3.40am and I'm getting very sleepy, I would have wanted to be with the liberating soldiers at the concentration camps helping the surviving prisoners to safety after the war ended. After all they had been through can you imagine what you would read in their eyes? That must have been something.
Thanks for starting a really great topic.

Teri