The Digital Library for Earth Systems Education is a good example of the potential for using the web as a community repository of educational resources.
Unlike some of the other educational websites I've seen (which typically distribute prepackaged course materials), the DLESE has a strong emphasis on community input.
Having been around since 2001, it has a pretty extensive selection of resources, most of them related to the natural sciences (from the Mars rover to tsunamis).
I have seen some discussion recently about the value of this type of resource in areas like New Orleans, where entire libraries have been lost. It's not difficult to extend this logic to the context of Liberia or Pakistan, though we have a little way to go before this type of resource is widely multilingual and accessible to teachers worldwide.
Have a visit: Digital Library for Earth System Education