Nations
Pick a different country each week and try a dish from there, learn a few words from their language, watch a film, take a tour of a museum or street view, and/or learn about a craft or art form.
There are folks doing a version where they're reading a book from each nation starting with with each letter of the alphabet in order.
A friend of mine who likes Formula One, celebrates each race by having a dish from the country that week's race is in.