A useful chart

[tamarinne]

This is a very interesting visualization of radiation, both from manmade as well as natural sources.  Note that this was done by a layman, and he makes no assertions about it being perfectly accurate.

http://blog.xkcd.com/2011/03/19/radiation-chart/

Comments

[learnedax]

I like the page he links to by his friend, for its slightly deeper discussion of dosage measurement. The presentation, however, is much better in his chart.