Official site -
http://www.animal-crossing.com/
Animal Crossing is sort of like The Sims. The basic storyline is this: You are about to spread your wings and travel to a new town to make something of yourself. But where you're going, you don't know. A cat, Rover, sits next to you on the train (all the characters aside you are animals, hence "Animal" Crossing) and tells you of a friend he has in the town you're going to called Tom Nook. He's a racoon who owns a shop in the town and is a real estate manager too. Tom gives you a choice of one of hour houses to live in (the other three can be filled with other human players) and finds out you're short 18,800 Bells (the currency) So you must work off your debt by working for him. After that it just carries on, him upgrading your house and you repaying your debt until you've paid it all.
You interact with the town's villagers (who are animals) and can talk to them, do jobs for them and more. You can collect things like furnirute, insects, fish, fossils, paintings and more. It runs in real time too, based on your Gamecube's internal clock, so if it's 2:00AM Wednesday 28th November 2004 in real life, it will be 2:00AM Wednesday 28th November 2004 in game too (and at that time, most of the villagers will be asleep

It's a lot more fun than it sounds.