Morrus, do you have particular criteria for choosing a charity?
Doctors Without Borders/Medicins sans Frontieres is a fantastic group that does fantastic work; they've got international appeal, and I've not heard of anyone who objects to them.
If you choose a medical charity, there are two caveats. First, make sure it's a group without ridiculous administrative costs. There are a lot of groups purporting to be medical research charities that give very little of your donation to actual research or other charitable aims.
Second, and this is probably not an issue here, but consider whether you want to donate to a charity that performs animal experimentation. Although it's an issue that I have mixed feelings on, having worked in research facilities, it's something that folks can feel strongly about.
Doctors Without Borders, being a group that crosses into all sorts of different settings, may be highly relevant to the product.
Daniel