When written well, science fiction and speculative fiction can open a window on current social structure and mores in a way that can profoundly change thinking without being overtly threatening. One of the ways these genres can do this is through the depiction of alien cultures. Think of Ursula K Le Guin's "The Left Hand of Darkness", for example. The way in which she explores gender and makes the reader quietly question his or her own gender assumptions was groundbreaking at the time the book was published. It probably had more influence on ideas about gender than many college lectures given in those same years.
Part of that is certainly worldbuilding and sheer writing skill, but some is also the way in which Le Guin has her characters use language to shape both their culture and our interpretation of that culture. One of my reader pet peeves is when writers simply omit contractions and have their alien races all talk a stilted version of English as a way to demarcate culture. True confession--in the first draft of the first novel I wrote, I had my Fantasy shapeshifters talk like that. At the time, I [cringe] thought it made them sound mysterious. Looking back, they just sound silly. Another peeve is the use of vernacular English with some simple substitution of a made up word for its English counterpart. (I think the Turkey City Lexicon calls this 'calling a rabbit a smeerp' problem.)
Language, culture, and thought patterns are intimately linked in ways we are only beginning to understand. For a fascinating example of this from current science, take the research of Lera Boroditsky. She is an assistant professor of psychology, neuroscience, and symbolic systems at Stanford University and was a guest on the WBUR show "Here and Now" on July 1, 2009 (follow the link and select the podcast to hear her interview). She is specifically looking at how language shapes the way we think.
If you'd rather read than listen, her article, "How does language shape the way we think" is fascinating.
In both the radio show and the article, Boroditsky presents some of her research. In one study, she looked at Aboriginals in Australia who speak in terms of the cardinal directions (N,S,E,W) rather than in relative terms (up, down, beside, etc). This is not simply a language pattern, but it is part and parcel of how they interact with the world and understand abstract concepts such as time. She also talks about how thought patterns about nouns are altered in cultures that assign gender to objects. A particularly interesting example of this is the word for bridge is feminine in German and masculine in Spanish. German speakers are more likely to describe a bridge in terms we associate with femininity (elegant, beautiful) while Spanish speakers use more masculine terms (strong, imposing.)
If you are a writer working with alien/invented cultures, I urge you to read Boroditsky's article and find the ways that your invented civilizations differ from our own in the way individuals think and use language, even if you never leap to the level of insanity of creating a complete language. (cough. . . Tolkien, LOL)
Follow the patterns of language and you will find your culture to be richer and more fully realized, making your story stronger.