Somehow, I'm surprised by all the German love in this thread.
Anyway, I was raised and still live in a part of the Netherlands where most people don't speak in standard Dutch but use a weird mix of German and Dutch, although I won't count this language as a 'language' ( although you can find dictionaries for it and what not ), it is because of this that I can understand pretty much everything said in German, I have no trouble reading it either, but I don't like writing in German nor do I like speaking it.
I'd like to think that I am pretty fluent in English, having one of those language proficiency certificates of the highest grade and what not. Got accustomed to the language through video games and television. Most movies being broadcast on Dutch tv are in English with Dutch subtitles, not only does this help children to learn to read fast, it also makes them familiarize themselves with the sounds of a foreign language, it is pretty nifty, maybe our eastern neighbors should look into it one day. *wink at germans*
Then finally there would be Japanese, I spent four years of my life majoring in Japanese and Oriental Studies, for some reason. Had some other stuff on the side as well, but it was mostly just studying Japanese in a casual, formal and business like setting. Even lived in Japan for about 9 months during my studies. So Japanese is also one of the languages I like to think I am fluent in, trying to play on the safe side so I tried a N2 proficiency test and passed it, so... yeah. Too bad those tests are so damn expensive...
So my languages would be: Dutch, German, English, Japanese
Did 5 years of studying French during middle/highschool, but I pretty much flunked every test because I couldn't be bothered to study, also did a year of Spanish, but that knowledge has long since left my head. And did 4 years of Latin during this period, pretty funny to see where some words come from in English / other languages.
As for learning a second language, I think that everyone should learn a second language, it is fun, will make you understand a certain culture better and well.. it is just fun.