I'm a language nut but I only speak English. I want to learn more languages someday. I took Spanish in high school and French in college but my Spanish sucks and my French is even worse. I really want to get good at Spanish someday. I could talk to a lot of people who don't speak English. It's one of my favorite languages to listen to. And it's useful here. There ain't much use for anything other than English, Spanish, or Choctaw in Mississippi.
I'd also love to learn Esperanto. Esperanto is a constructed language designed for world use. Esperanto.net gives more information and Lernu! offers Esperanto courses. I've looked at Esperanto a bit. While it's nowhere near perfect, it's still better than English for a world language. Sometimes I forget how much privilege I have that my native language is the standard world language.
As always Wikipedia has a good article on Esperanto and other related conlangs such as Ido and Novial.
I have my Facebook in Esperanto right now. Google Chrome keeps flagging the page as either Slovak or Spanish. Makes sense because Esperanto's a mashup of Slavic languages (Slovak, Czech, Russian, Polish, Ukrainian, Belorussian, Slovenian, Serbo-Croatian) and Romance languages (Spanish, Portuguese, Catalan, French, Italian, Romanian). Back then the rest of the world wasn't part of the world. I'm learning a few words from Facebook, but I'll forget most of them when I switch it to some other language. I should switch it to Spanish or French for fun. I've also done Welsh, Latin, and a few of the joke ones like Pirate and 1337.