The non-profit organization Food for the Poor has been installing (and trial-testing) waterless toilets in remote parts of Jamaica and Haiti.
How it works: "The system separates liquid and solid waste as it enters the toilet bowl. Liquid waste drains to the bottom of the container, while solid waste remains on the drying plate. Both are exposed to a continuous flow of air. As the air moves through the system it dehydrates the solid waste as it migrates down the drying plate, and causes the liquid to evaporate quickly. The negative pressure within the container prevents the escape of any odor through the toilet bowl or through the air inlet pipes. The odor is vented into the atmosphere via the wind driven extractor."
(Sorry if that was TMI, but it made me appreciate my flush toilets.)
More about the Enviro Loo here.