My French and Mandarin Chinese are rusty from years of disuse, but there were times when I had mostly fluent basic conversations. I studied five years of both languages, and lived and/or traveled briefly in France and Taiwan. Even today, I'd still manage basic conversation, but with stumbles.

I also understand a lot of Czech, but have a long ways to go inorder to speak it conversationally. I live in Czech Republic, so there's little excuse for avoiding intensive study. I have been exposed to bits of German and Spanish, along with very brief past study (months each), but only now remember handfuls of words and phrases in those languages.

Is there a subject you studied in your youth that you wish you had pursued further?