http://orbit.medphys.ucl.ac.uk/Learn orbital mechanics while going, "Oh look Wow, that's so pretty!"
Been playing this for a long while. As a casual Friday night challenge, it was off to the ISS from Kennedy and back. Managed to get into "normal flight" about 10 miles North of the runway and with my joystick disconnected, I choose a hover approach, right onto the numbers.
Allows you see the detail NASA et.al. go to, but realise that ball park works so well, just less efficient.
Rendezvous (with the ISS) is probably the hardest thing to wrap your head around. 80% of intuitive goes out the window, you just have to know which 20% to trust.