Yayasan Usaha Mulia, the NGO where I work, is currently looking to create a t-shirt that we could use during events and also to sell. I've been looking around several websites and fell upon Threadless which is an online shop for t-shirts but the shirts are designed by the public so anyone can submit a design. But the great thing about Threadless is that it has a special page for t-shirts designed for causes, such as Unicef, CARE, etc. I think it's an amazing idea and wish YUM could team up with them though I don't see any NGOs outside the United States.
Anyway, I just wanted to share what I just discovered, and if by chance you're a designer, we'd love to have your design for a YUM t-shirt! Email me: firstname.lastname@example.org if you're interested :)
This design was under the theme "Empowering women to change their world". You can see more t-shirt submissions at: http://atrium.threadless.com/CARE/
This design was under the theme "Freedom". You can see more t-shirt submissions at: http://atrium.threadless.com/dnafoundation/
This design was under the theme "Childhood". You can see more t-shirt submissions at: http://atrium.threadless.com/unicef/