I'm the kind of person who knows useless knowledge but sometimes lack "common knowledge". For instance, I don't know how many hog heads are in a gallon, or the prefix codes for Quam, or the proper flag signals for an industrial crane. I tell you, it can be almost embarrasing in certain circles.
One night while watching Mythbusters, Jamie, one of the hosts, mentioned the little black book that should be in everyones tool box. It was called 'The Pocket Ref'. It contains endless amounts of useful information and rounded out with "useless" info. Perfect for anyone from engineers/technicians in various fields to Alcaholics sitting on a bar stool arguing about the weight of Carbon (sounds like my average workday).
I bought one at Borders (despite going on the web and their website saying they were out of stock, the person at the desk saying they had one copy in General Fitness, and the person who showed me where it was saying "that has nothing to do with refereering") for only 12 bucks. I've had it only a few weeks now and have used it on quite a few occasions.
I like to say its a book that contains everything you should know, but don't have the time to remember, and a book you must have near you when you don't have access to the internet (i.e. a barstool). Go to your local book store and buy yourself a copy. Its priced right and is a fun page turner.