I am considering a new house rule for my fantasy campaigns: Nearly all beings capable of speech speak the Common Tongue as their native language. It is truly the universal language. Accents and colloquialisms are the only true variations in spoken communication. Writing is another matter, however, for every people and species with literacy has its own unique system of writing for expressing the same language. Any language bonus gained by high intelligence or species refers to the written language only.
This may seem absurd at first, but is it any more absurd than a fantasy adventure where social interaction would be limited to hiring interpreters or resorting to pantomime? Think of it in terms of the universal translator from Star Trek or the semi-telepathic communication on Barsoom. Would we really want every encounter with a new civilization to be burdened with a new invented language and a long period in which the story stalls whilst everyone takes a course on Tholian or Gorn or whatever happens to be the alien of the week? Yes, it's unrealistic, but it's no more implausible than replicators or warp drives, and it allows the characters to interact in much more interesting ways. The Martian tales by Edgar Rice Burroughs are teeming with exotic sentient species, but how exciting would it be if John Carter had to spend months learning the language of each one just to have a rudimentary conversation? The Martian tales are, incidentally, the inspiration for a world where there is one spoken language with a multitude of written forms. It makes perfect sense for a world of exploration and swashbuckling adventure.
After all, what is being sacrificed by the absence of spoken Goblinish or Trollish at the game table? Those languages are not really being spoken. The referee generally just says that the players fail to comprehend, or blathers nonsense syllables. And the suggestion of using multiple real world languages just destroys immersion and presumes a knowledge of more languages than is reasonable to expect of most gamers (not to mention the referees).
It may not be the perfect solution, but it impedes role-playing the least, which is why I think it may be the best solution.