Birding, in which I attempt to see, identify, and [photographically] capture every bird species. This is no walk in the park (well, sometimes it is). There is a big leap from seeing to identifying, and from seeing to capturing.
Learning Japanese, in which I study different aspects of the Japanese language (reading, writing, speaking, listening) with my American adult brain. No, I do not watch anime (2021 edit: …regularly).
Music: guitar, saxophone, oboe, singing, …
Running.
Visual computing, in which I attempt to make computers interpret visual content like humans do (except better), and create aesthetic images with the help of GPUs.
Writing, in which I read good books and draft bad stories.
Bonsai, climbing, dancing, disc golf, drawing, geography, letter-writing, photography, soccer, sewing, swimming, …