woodchanges.com is a website that visually represents of the change that occur in wood over a variety of variables. Of course the theory behind it all lays in the fact that wood is a hygroscopic material, such that it exchanges moisture with its surrounding environment (As a piece of wood looses moisture it shrinks and as wood gains moisture back it swells).
Here are a few screen shots of the charts displaying information over 12 months in New York.
Temperature, Humidity and Moisture Content
Wood Absolute Dimensional Change
Wood Relative Dimensional Change
This kind of information is extremely valuable for furniture makers or wood workers who may find their products crossing international boundaries.