Here's the ones I use most often: Avinor (Norwegian airport authority), Schiphol (Closest hub), Kastrup/Copenhagen (#2 hub (of sorts)) and Frankfurt.

Then there's all sorts of second tier airports which have their own apps of sorts - say, even Dyce (Aberdeen) has one, though I am not sure it is an official product.

Add to that that any airline worth its salt has got at least one app, and it soon adds up...