It seems contrary to the whole idea of Bitcoin to have someone else handle payments for me when I can easily do it myself. Perhaps a better effort would be to maintain a list of Bitcoin-accepting charities if one doesn't exist yet, plus what Salty suggested. Also there might be some inconveniences with pooled funds depending on local laws and regulations - larger donations could trigger reporting requirements for the charities, individual donors might not be able to use tax deductions unless the fund itself is a charitable organization, etc.