Doctors Without Borders has a very clear logistical plan.
World Vision describes their work on the ground.
Mercy Ships is sending a supplied ship from Texas tomorrow.
The Salvation Army can take $10 donations if you text "Haiti" to 52000.
Save the Children also has workers on the ground, setting up mobile clinics and bringing medical supplies.
International Medical Corps is providing emergency surgery including amputations. They have converted part of the hotel where they're staying into a makeshift clinic.
Catholic Relief Services is trucking supplies in from the Dominican Republic. Their people on the ground are working to get a damaged hospital back into operation.
More information about relief agencies and what they're doing to help Haiti is available at the Huffington Post.