Warning about astronomy classes, though - it's a lot more physics and a lot less NOVA than you would hope for. I know from experience.
I did not take the lab despite my university having a world-class planetarium, so maybe that's my fault.
I hated school, though I love learning. I was always bored. I'm planning to teach a class at UNC after I "retire," which I hope is in the not too distant future. At least that's what Tim Ferris says.
To pick a class, I'd look at the type of thing you spend the most Wikipedia time on and find a class that specializes in that type of thing.