After speaking with someone who's actually headed down there she suggested in the strongest of terms to donate your cash to the Salvation Army. While there are many safe and reliable conduits, the Salvation Army has a strong track record in Haiti and they guarantee 100% of all donated funds go directly to those in need. No administrative costs or any of that other non-sense. Also, I like the idea that they have no political agenda one way or the other.
In addition to Care, the Salvation Army, and other highly reputable humanitarian agencies, be sure to consider supporting the National Medical Association (NMA) which represents some 30,000 black physicians in the US. The NMA responded swiftly in assembling a Gulf Coast Task Force during Hurricane Katrina. Their medical response to the challenge in Haiti is already underway. http://www.nmanet.org/index.php/HaitiRelief/donateform