This KML network link displays all GPS traces that were uploaded to http://www.openstreetmap.org/traces as a map overlay in Google Earth. Colors denote direction and please have a look at this blog post from mapbox for more explanations on this layer.
For some information on how it works, please see the main page and the FAQ.
To get started, simply download all 10 OpenStreetMap map overlays on this site.(please log in first, see here why) and open it in Google Earth. Or checkout
Do you have comments, bug reports, or suggestions for other map sources? Please leave them below.