What programming languages can one use to develop iPhone, iPod Touch and iPad (iOS) applications?

Question

What programming languages can one use to develop iPhone, iPod Touch and iPad (iOS) applications?

Also are there plans in the future to expand the amount of programm

Answer 1

This might be an old thread, but I'd like to mention Appcelerator Titanium, which allows anyone versed in HTML5/JavaScript/CSS to develop iOS applications.