What’s the most useful non-gaming source of information (book, website, etc.) you’ve ever found? And what makes it so darn useful?
Online, I have a few resources I use… for wildly different reasons. I like What a character.com for its Chraracter Actor pictures. I don’t visualize clearly enough to describe people, most of the time. This helps- or gives me a picture to pass around. Other goodies include the CIA World Factbook, for useful maps and facts. The last commonly used resource is a tarot spread, like the one from Web Tarot.org, since I don’t do readings at all well by hand, but still find them useful.
Offline, a good map of the city (for a modern day game) is ideal. The best maps are tourist ones– they include landmarks of note and help give you a clear idea of a place, plus they suggest names for further research and investigation.