I got an email from Austin Meyer's list today. If you don't know, he's the guy who has been competing with Microsoft Flight Simulator for many years with X-Plane. There are several versions now for the iPhone or iPod Touch, that are very impressive.
I just saw that there is soon a space shuttle simulator for the iPhone coming out very soon. I'm looking forward to adding this to my iPod Touch. I'll try to post a review once it comes out.