PlaneFinder.net is a surreal website that shows you in real time the planes flying in the sky. And there's a lot of them! It makes me feel really small when I think about all those aircrafts and the millions of travelers flying over my head my right now. I'm also quite jealous because I'd love to be in of those planes heading to an exotic destination...
If you click on a plane on the map you will get details about the route and some info about the aircraft (airline, type, etc...) and even a nice visualization of it. You can also filter the main map by airlines or even search for specific flights. A good way to check if people are going to be later before you go pick them at the airport.
One thing that I noticed on Plane Finder is that you can't see any planes over the oceans and seas. So I checked the page that explains how the map works and learned that it uses land receivers that listen to the feeds coming from the planes close by. But obviously none of those receivers are in the sea.
Head to the website and become a plane nerd too!