Along with collecting paper ephemera, and stamps, I like to collect money. (Perhaps this idea came from my mom, because she has quite the European money collection.) Whenever I travel outside of the U.S. I have this little checklist of #1: get stamp in my passport (even if they don't do it regularly, oh I've got some great stories about foreign consulates) #2: pick up some local paper currency and #3: find some local stamps.
Like stamps, money is a unique way for countries to express their culture, art, and nationalism, and it is usually done so incredibly beautiful. Look at these gems that my friend recently brought me back from Cambodia. He brought lots of various kinds and even some that aren't supposed to exist. Thanks Gavin! I have found this shop on ebay a fun place to peruse.