It's my favorite charitable option because it directly supports grassroots Haitian social movements that are committed to both immediate relief and systemic change. (None of us will need to be reminded that there's very little "natural" about the Haitian disaster, I think.) Its ratings from the Better Business Bureau, Charity Navigator, and Independent Charities of America are reassuring too.
For our less-political friends, any of the organizations given four stars by Charity Navigator are excellent choices:
http://www.charitynavigator.org/index.cfm?bay=content.view&cpid=1004
Many more-political, not-quite-radical types are particularly fond of Doctors Without Borders, Oxfam, and Partners In Health. They'll at least speak openly about things like military occupation and international debt, even if they don't do much work around them.
Before anyone asks, I have no ties to any of these organizations, beyond having occasionally given small sums to a few of them.
-- "Hige sceal þe heardra, heorte þe cenre, mod sceal þe mare, þe ure mægen lytlað."