I have heard it suggested that atheists are somehow less supportive or active regarding support for charities. This has not been my experience.

Maybe Non-Prophet Week should be organised in conjunction with Christian Aid Week, which is what might have inspired the idea.

http://en.wikipedia.org/wiki/Non-Prophet_Week

I don't think the American Humanist Association have a non-prophet week, but they do initiate and support a number of charity events.
http://humanistcharities.org/

http://www.ahsstudents.org.uk/nonprophetweek/

Non-Prophet week: 29th October to 4th November 2012.

Just FYI