Well, since everyone else are doing, I'll join in with my own travels as well
Much of Europe (live in Denmark, been to Sweden, Norway, England, Belgium, Germany, France, Italy, Austria, Cyprus and Greece), Uganda (my first trip outside the continent) and Texas (1 month long schooltrip.)
I'm really happy that I've been away and seen other countries. But I want to go see these countries with myself being responsible too, because you don't experience much of the culture when you're young. Uganda and Texas were the two trips that made the greatest impressions on me, mostly because they are so different from what I am used to. I'd love to go back to Africa and see another safari, or go back to the US and actually experience a real football game.
When I went to Texas, it was with my highschool class (not really highschool, but it's the closest to it I think), and we had a blast. We went to school (specialized for us though, so we didn't get to meet many people of our age unfortunately), and we went to see a lot of different things, it was really great!