If you ever had any doubts about the power of crowdsourcing, or simply about willingness of hordes of anonymous strangers to commit time and resources just to a cause, totally for free, have a look at the following video. It highlights a year of edits of free OpenStreetMap data.
OpenStreetMap: A Year of Edits 2011 from Derick Rethans on Vimeo.
Many question the quality and “authority” of the data but personally, I am very impressed with accuracy and currency of data, where available. Great free resource. Great cause!