Source: http://vizual-statistix.tumblr.com/post/...

Have you ever wondered how fast you are spinning around Earth’s rotational axis?  Probably not, but now you can find out anyway!  This graph shows the tangential speed of a point on Earth’s surface for a given latitude due to Earth’s rotational motion – it does not include speed due to our revolution around the sun! Tangential (linear) speed is the magnitude of the velocity vector, which points tangent to Earth’s surface in the same plane as the circle of latitude.

I’ve plotted the dependent variable (speed) on the x-axis; though this is unconventional, it allows the map in the background to be placed in the traditional north-pointing-up orientation.