I thought I'd start this off with a bit of nostalgia and post about my first official postcrossing postcard received. It arrived on the 22nd of November 2007 from Switzerland, from the lovely Zasa. I remember being very excited to receive the card - someone had made it specially for me, and written it full of nice text.
This was the stamp on the card. It shows Leonhard Euler, a pioneering Swiss mathematician and physicist.