I got a handful of great responses in my earlier Flickr Pro giveaway thread. I love the idea of repurposing flickr for a wedding photographer -- you could use the private gallery options to show photos to clients and keep the negatives. I love the idea of helping out budding photographers, limited by the free account's storage boundaries, I've always felt artists should never be limited by tools.
But I love helping non-profits more, so I have to give the top nod to the Free the Slaves site. I think having a way to email photos from the field or from members worldwide could really shed light on their work and hopefully help end the practices of forced labor and child labor.
Several others said they might give away their extra flickr pro accounts to other posts in the thread, so if you hear from a random stranger about it, that's why.
Oh, by the way, if anyone from the Free the Slaves site could email me their flickr free account name, I can then upgrade it to pro status.