Science fiction writer and/or working in biotech.<p>My degree was in biochemistry... that's what I thought I'd be doing, but there was no demand for more entry-level biotech workers when I graduated and lots of demand for programmers. That being said, I think I enjoy programming more than biotech.
I would be coding for fun :-) Working in languages and toolchains of my choice (Clojure, f.ex.), helping organizations worth helping (NGOs,...). But that would be only a part-time activity, I would use the other part for stuff I like & never have enough time for - yoga, teaching, ... .
Maybe it is still the kid in me but professional racecar driver. I use to tear cars down and build them up when I was younger. I never have the financial/family support or knowhow to race full time.
Hmmm. Maybe I would try to gather some money for creating a music instrument shop/service. I like music and technology (behind music) as well - that would be fun!