My Pocket Ref just arrived in the mail (thank you Amazon Prime). I thumbed through one of these once at a friend's house while we tried to figure out how to tie a certain knot, but I had forgotten the name. The other night I saw it on an episode of Mythbusters so I immediately ordered it.
I'll probably never need to decipher proofreader marks, convert furlongs to feet, or signal a crane operator, but I've always been the sort of person who enjoys having that kind of data at my fingertips. Google and the web are still great for finding nuggets of information that possibly answer your question, but there's always that moment of deciphering and extracting what you were looking for. Pocket Ref features simple tables and entries arranged in a very readable manner that still beats the web. And you can put it in your pocket.