I'd Google Samaritans Purse, they're not quite the unmitigated good cause they seem to be thought of as. They're evangelical as they come and I know of a fair few moderate Christians who think they're a bit scary.
The idea is solid enough though, and there are other charities that do similar things without the evangelical overtones (
http://linktohope.co.uk/shoebox-appeal http://www.aquabox.org/). Of course, giving actual money is probably more effective, but I realise that's not necessarily a straight swap.
