This thread is relevant to my interests. (Surprise.)
I've cached in Portugal, Spain, Scotland, Ireland and the US. And--gasp!--it's much easier after you acquire a GPS unit.
Love to go caching with the fiance at night in the middle of the desert, even when the hints are something like "pile of rocks by yucca".
Favorite finds so far include a pinecone, a magnetic strip perfectly camouflaged on a roadblock sign, a fake metal plate added to a technical box, a fake rock, a snail shell, a cache called "Well Done or Half Baked" where the container was inside an old oven, and a multi-cache about "heroes, villains and justice" that had a logbook which was essentially a laminated superhero comic book. There is a multi-cache in Edinburgh that took me down the Royal Mile, with intermediary points related to gruesome events in those locations. Macabre, but deliciously fun, and a new way to view the city. I really like the places and stories you go through while seeking a cache.
...in between, way too many film cannisters and altoid cans tucked into impossible locations. And those diabolic nanos that are the size of a fingernail.
Trying to clear as many of the Lisbon caches as I can in the months before I leave the country. It's always a good way to spend an afternoon.