I believe that learning new languages is always useful. First and foremost, you can increase your cultural competence. Secondly, you may expand the geography of your contacts. Finally, yet importantly, you can enjoy communicating with foreigners in their native language. Thanks to the Internet, numerous resources (free and for purchase) can be found. I will not discuss the best way possible to learn another language in this topic. For the general idea, visit the Antimoon website. Instead, I would like to merely share my experience on some “exotic” ways of learning a foreign language.
Learning new words
Presuming that it is reasonable to learn words that are in common use, one could suppose that it could be worthwhile to find the most frequently used words in a certain language. Such a list is actually provided by Wikipedia. I cannot say that these words are the most important words one should learn, but it definitely might be good to start with them if you do not have any other sound alternatives. At the similar research project website you can actually see the popularity of English words in the live mode.
My good friend wrote a tiny yet useful desktop application that takes a .txt file as input and outputs another .txt file with each word met and the number of this word appearance in the text. Denis added a really useful option of creating a list of exceptions – words that will not be counted – for example, “a”, “the”, “and”, etc., since those words are by far the most commonly used in almost any English manuscript. I see a great application for this utility. For instance, one can discover which words are the most often used in a book one likes and try to learn them if one does not know them yet. On the contrary, an advanced learner could go in the opposite direction: it could be interesting to check the words that were used very seldom or maybe even once. Naturally, one could skip a certain geographic object name of little importance or a hero name of a novel since those words do not have much of value for a learner. Another application for this utility could be found by students. While having a text file of a book (on the topic of spatial database development, for instance), one could find what terms or definitions one does not know and focus on learning them (especially if only one hour is left before the examination!). Likewise, one could use the list of the most commonly used words to get at least a general perception of the topic sense.