Most of my spare time is spent organising and participating in science fiction conventions worldwide. In the last ten years I have chaired four conventions (ranging from 50-500 people each) and have worked on dozens more, including for the Tolkien Society (of which I was Treasurer for several years) and the British National Science Fiction Convention.
(Note: not all conventions involve costumes; this just seems to be a prerequisite for people taking photographs.)
Science fiction conventions provide captive audiences of laypeople with strong interests in astronomical topics. I have given talks at conventions on subjects ranging from black holes and relativity to exoplanets. I also been involved with children's science programming at the World Science Fiction Convention, where I have learned that children as young as seven can understand A-Level Physics topics if they're presented in the right way.
In September 2012, I drove the entirety of the Historic Route 66 from Chicago to Los Angeles (plus part of the Pacific Coast Highway up to San Francisco). The trip was extensively blogged for posterity, providing eternal photographic evidence of sunburn and desert hair.
And if there's any remaining time in which I'm unchained from my desk, I can usually be found patronising theatres up and down the UK or in New York.