Retro computing. Currently, I'm categorizing any computer or gaming console more than 15 years old as "retro" but I've been playing with Mac SE/30s, 1999 to 2005 era Sun Microsystems workstations and servers, and PDAs that came out between 1996 and 2001. Old DOS programs and PC games from the 80s and 90s, etc.
Amateur radio, but specifically digital modes including DMR, Fusion, APRS and mesh networks such as AREDN
GMRS, which is kind of like a paid-license limited ham radio or high-powered FRS, but without having to pass an exam (we have several GMRS repeaters and a growing GMRS community around town)
Automotive repair and car hacking
Quadcopters -- flying them, aerial photography, hacking them, FAA Part 107 certification studying, etc.
Electronics repair
Basic wood shop stuff, building things. Although with lumber prices I haven't done a lot of it lately.