So I was wondering where I could find a list of how fast things go in terms of orders of magnitude, and I managed to find one on Wikipedia.  This will definitely help a lot in estimation calculations.  Other articles for orders of magnitude exist for other quantities like length and heat capacities.  Below are some links for some of these quantities.

Speed: http://en.wikipedia.org/wiki/Orders_of_magnitude_(speed)

Mass: http://en.wikipedia.org/wiki/Orders_of_magnitude_(mass)