Another vote for SkyDemon in the UK and Europe. In the UK you can enter a six digit postcode and it gives you a list of adjacent airfields and a spot on the map.
They currently have charts for Europe, big bits of Africa, USA and NZ. I understand more are on the way.
Once you use SkyDemon in anger you realise that it is simply a generation ahead of anything else out there (and I have tried most of them). Game-changer.