Here is their existing logo:

An open competition has been declared to design a new logo for the organization. Anyone can participate. The logo is to be universal in culture and has to achieve a global acceptance.
It is to be designed in all color format, CMYK colors for web publication or color print, gray scale design for press etc.
The submission will be via email in any vector format, although JPG or PNG format is also accepted.
The top ten designs will be awarded signed first editions of ‘Design Like You give A Damn: Architectural Responses to Humanitarian Crises’ and the winning design or team will receive $1000. A jury will select the winning entry and all results are final.
Submission deadline: December 15 2006
Please visit
http://www.architectureforhumanity.org/logo/
for detail.