Global Health eLearning Center
The Global Health eLearning Center was created as a resource for USAID workers but is an excellent tool for anyone involved in global health. Registration is free and the content is varied and useful. Focus your study by taking a certification course that highlights one particular facet of your international work. I would highly recommend this fabulous MPH resource.
Check out Resources for MPHGrads to find other useful gems to help you make a difference in the world.