If you are on a short trip and do not want to waste time finding a postcard and stamps, or if you just want to send a very personal postcard, use a phone app!
For danes Post Danmark has the Postkortet App’en, for iPhone, Android and Windows Phone. It simple and easy.
I have also tried Popcarte, only for iPhone and Android. If the internet connection isn’t the best where you are, make an account with Popcarte beforehand.
With both apps you just take a photo on your phone, write a message and the address, and then 3-4 days later the lucky person will get the personalised card. Nice and simple 🙂