Start with the National Hurricane Center, which has lots of different maps of Hurricane Matthew’s predicted path, weather warnings, rainfall potential and so forth. See also maps from Weather Underground.
Google’s Crisis Map includes evacuation resources—Red Cross shelters, evacuation routes, traffic data—in addition to storm track and precipitation information.
Matthew has already struck southwest Haiti; the Humanitarian OSM Team has put out a call for crisis mappers on the following projects: buildings in Nippes; road network in Grand’Anse and Sud.
Wind maps from Windytv and EarthWindMap visualize the wind patterns of Matthew and, further out in the Atlantic, Nicole.
Hurricane imagery from NOAA’s GOES East satellite. NASA Earth Observatory has imagery of Matthew’s path toward Florida.
[Dave Smith/Maps Mania/NASA Earth/NOAA Satellites]