Such a massive natural disaster in a country which was barely able to provide basic medical care under normal circumstances.
I don't think that money is a major problem right now - charities have enough funds for emergency use. Donate, but don't rush your decision to whom and how much you should donate. The big problem is logistics. I've thought about it, and it really is horrible.
The UN headquarters are destroyed, and most of the senior staff is dead. Many hospitals have collapsed, even the president of Haiti doesn't have a place to sleep anymore. Newest sources seem to suggest that the airport in Port-au-Prince is closed for air traffic. How you're gonna help if there's no way into the country?
Seems that US forces offered to take over air traffic control, but I couldn't find a timeline. The US are also sending the USNS Comfort, a very large hospital ship, among a host of different vessels. But it takes 5 days to make the ship ready, and another 5 to reach Haiti. I don't want to think about how many people will already have died of otherwise treatable injuries by then. Many countries are also sending SAR teams. But... 3 million people affected, and a few planes with rescue personnel to search for people trapped under the rubble? A drop in the ocean.
Not to mention the lack of food, police, shelter and hygiene products. Diarrhea is at most discomfortable in the western world, but could be the major cause of death in the aftermath of this earthquake, along with deaths accounted to bad hygiene. But I hope the infrastructure is sufficiently restored at the point where this becomes a major concern.
So to sum this whole thing up: It's a disaster, on a really large scale.
My thoughts are with the victims.
edit: Sub_umbra: at least they seem to have a level of coordination between the different GO and NGOs now, as a result of the 'suboptimal' planning and communication during the Tsunami disaster. And corruption.. well, the Haitian government seems so nonfunctional that the president might give wide-ranging authority to the UN. That's at least what I hope for.
Another problem I see is people, in an act of blind actionism, donating way to much money. The biggest charity in Switzerland received massive amounts of money during the tsunami disaster, and they had no idea how to spend it. In the end they've built a complete village... which no one wants to live in. Meanwhile, people in disaster area of low intensity and thus low media value are still suffering, and actually receive less help, because people donate for a specific purpose only, instead donating to the charity in general.