Sort of an "out there" question: Fluid dynamics sounds interesting. Is there any, eh, "fun, interactive" fluid dynamics simulation thing I could check out? Basically, playing with someone else's model instead of modeling things myself
Lately, programming for a company that does online surveys. It's not glamorous, but it is data analysis and intellectually challenging enough. Other than that, I've worked on the Rakudo Perl 6 compiler. I help run a nonprofit wiki farm at miraheze.org, where I'm the security specialist. And I'm getting sidetracked in politics once again.
Too many side projects means I wasn't really focused enough to get a graduate degree, but hey, you have to live life as you want, and go after the things that make you happy.