From Intelligence and Terrorism Information Center, May 26 2010:
IHH, which plays a central role in organizing the flotilla to the Gaza Strip, is a Turkish humanitarian relief fund with a radical Islamic anti-Western orientation. Besides its legitimate philanthropic activities, it supports radical Islamic networks, including Hamas, and at least in the past, even global jihad elements....
Follow the link for a detailed Portrait of IHH
Also go to the following 1 June 2010 postings on NGO Monitor, for more on IHH and other NGOs involved.