Another interesting one is pi: http://www.google.com/trends?q=pi

Ignore the spike near 14 March and look at the log low dip in summer and the sharp upslope in August-September.

Other very seasonal queries: http://www.google.com/trends?q=mushrooms

Also, for some reason, "DYI", "pi", and "horses" all had large spikes around the end of 2007. Anyone want to guess why? Data gremlins?

http://www.google.com/trends?q=diy%2Cpi http://www.google.com/trends?q=horses%2Cdyi%2Cpi