"Intuitive user interfaces often use metaphor as an effective 'vehicle of exploration', according to David Siegel in Creating Killer Websites. His examples of metaphors include: 'galleries, TV remote controls, magazines, tabloids, store environments, museums, postcard racks, amusement pars, going inside things (computers, human body, buildings, ant farm, and so on), safaris, cities, and cupboards."

-David Whitbread in The Design Manual

Also... check out Microsoft Bob.