Spanish and Norwegian
I have learned both Spanish and Norwegian as second and third languages.
I began learning Spanish in High School, using a traditional academic method of studying verbs, sentence structure, and grammar by using textbooks and not much else. I found it very easy to pick up, and was frustrated with the slow pace and repetitive nature of all my classes. So much so, that I worked ahead with my teacher so that I could skip a level.
This was unsuccessful, however, because the school was not willing to test me or otherwise prove that I could be successful in the top level after skipping the previous one. This made things even more frustrating, as then I was stuck in a class where I already knew the material!
I went on to college where I then used the language extensively both in and out of the classroom. I studied literature, culture, and Spanish linguistics and very much enjoyed the cultural and linguistical elements, but found the in depth study of literature to the near exclusion of all else a very unbalanced way to study.
I got the most out of using my Spanish outside of the classroom, including a trip to Costa Rica with a church group, where I found myself being utilized as an interpreter. It was certainly challenging, but it was also a lot of fun.
I then also volunteered to be an interpreter in the community schools and also used my Spanish teaching English to Spanish speakers. This is probably where I learned the most!
In college I also studied Norwegian just for fun. Having already mastered a second language, I found learning a third was incredibly easy. I routinely astonished my classmates by picking things up immediately, while they were struggling to learn the material. I believe this is just because I had already learned a second language, so learning a language had become easy to me as it may not be to someone only fluent in their native language.
What I really liked about learning Norwegian was that the instructor used the language from day one. We had to listen carefully and absorb the language by hearing it and taking in visual cues. We also used songs and videos to get a taste for the culture as well as the language.
Sadly, I rarely have use for my Norwegian, other than the occasional translation of Danish for genealogical research, but I'm still very glad I learned it, and hope to use it one day on a trip to Norway.