One Response is an organization that is coordinating or assisting with data management many of the international bodies that are providing disaster relief in Haiti. They just put up this map showing where populations are moving within Haiti. The data, however, is likely a large undercount as it is just the number of those using government funded transportation out of the disaster areas. Also, the data is not very precise as it does not show which of the various cities or Communes in the Departments are seeing population increases. However, this is a start and very important data. One Response has a vast collection of information on the relief efforts here(much still in development). Definitely a place to watch for essential information.