Thanks for the responses!

Probably Spanish would look best on a résumé, but I almost never meet Spanish-speaking people who don't also speak fluent English (here in Wisconsin), so I'm not sure how useful it would be to me. I also can't think of any Spanish literature or media which might interest me. I feel like I would never use Spanish once I complete the required courses.
Sounds like Chinese is very difficult and likely not very rewarding, so now I'm leaning toward French. There's a ton of French film and literature which might be interesting, and there seems to be quite a few French-speaking people involved in P2P projects like Bitcoin, Freenet, and I2P, so French might be one of the more useful languages for communication I'm likely to engage in.
As a Chinese, I'm willing to remind you that learning Chinese is not that rewarding as learning IndoEuropean languages. You should be prepared that after one year of study, you will be still struggling reading element school level materials, while your friends who chose French are already happily reading Bastiat without any difficulty.
Not because Chinese is intrinsically harder. It's just too different from English in almost all aspects.

Ah, I hadn't realized learning Chinese would be so slow-going. Being unable to read anything substantial would make learning the language much more difficult, I'd imagine.