I love Ghost. A lot.
Some other games:
Encore - Someone says a word or category (e.g., "Boys names A-L" or "Colors") and sings a song with that word in it. Go around in a circle until someone can't think of other songs with that word in it. That person drops out and the game continues on until there's only one left. (or you can have two teams). Whoever wins chooses the next word (or whoever loses first...). I should note that this is a purchasable board game, too, but the only thing that really gets you is the words.
Geography - First player says a place name (city, continent, body of water, neighborhood, whatever). The next person has to think of a place name that hasn't yet been mentioned that starts with the last letter of the previous place. The game continues until you get mind-blowingly bored. E.g., "France", "Epcot", "Tokyo", "Oceania", "Aral Sea"...
The Chinese Restaurant Game - This is a game my brother and I made up at a Chinese restaurant, hence the name. Feel free to call it something else (maybe "Free Association"). One person thinks of two words or phrases. The other person has to get from one to the other one step at a time using words that somehow connect in whatever way makes sense. The fun is explaining the weird connections your brain makes. For instance, "Dog" and "Cinderella" can be (among an infinite number of paths): Dog => Puppy => Guppy => Fish => Fishbowl => Glass => Glass slipper => Cinderella.
Twenty questions/Many questions - One person comes up with a noun of some sort (physical things work best). The other players are guessers - they try to figure out what your noun is based on yes-or-no questions. The first question is always "Animal, Vegetable or Mineral?" - Animal if it's a person or animal, vegetable if it's a plant, mineral if it's anything non-living (water, computer, volcanoes, and sky all fit into this category). The guessers continue to ask questions ("Is it round?" "Can I hold it in my hand?" "Have you ever eaten one?") until either (a) they have correctly guessed the answer ("Is it the moon?") or (b) they run over the limit of questions. IMO, this game usually works best if you have infinite questions and you use rather obscure answers (venetian blinds, Jean-Claude Van Damme, Stonehenge, etc.)
Going on a Picnic - One person comes up with a criterion for judging words (to be explained). The person says, "I'm going on a picnic and I'm going to bring X, Y and Z," where X, Y and Z are three words or phrases that match the criterion. The other players ask, "Can I bring a Q?" to which the judge says yes or no based on the criteria. The goal for the guessers is to figure out what the criterion is. The criterion can be based on the actual properties of the object (e.g., "things that are bigger than a bowling ball") or on the properties of the words (e.g., "things with double letters").
MindTrap - MindTrap is a really great thinking game that you can buy cards for. The driver doesn't need to see the cards - she just needs to participate in the question asking.