In spite of the needs of developing countries, experts from abroad often propose solutions based on technologies from developed countries.
1. has many followers in Laos as a local silk company has been giving workshops in making the filters at the same time they teach villagers about silk production methods. It's a concrete box filled with sand - the water gets purified as it sinks through the sand. Like natural ground water peculation, the micro-organisms that grow in the sand help to ripen it, making it more effective in filtering the water. Strangely enough, chlorine treated water is not cleaned as well because the chlorine kills the micro-organisms and beneficial bacteria. There isn't enough research yet to know if viruses are killed in this system.
2. Solar systems - in Laos, Sunlabob (meaning 'sun systems') is a renewable energy system based on solar power. It got its start in Laos, and has been accepting contract work, bringing its ideas to other countries. It has won several development awards for its low cost systems. In Laos, they have been working on mixed energy systems - using both small scale solar electric generation as well as generators and small hydroelectric systems for use during the rainy season when there is not so much sun.
3. Solar Cookers - I remember seeing this technology back when I lived in the US. There have been attempts to introduce it to Laos but it really hasn't caught on. With any kind of development work, cultural practices have to be addressed and sometimes the culture takes a while to get it. Some projects have gotten acceptance in Africa - link.
4. While I can't find any references - there is a common sanitation system used in Laos, similar to the sand filtration system. A septic tank is built in three sections - the waste running into one end, which percolates up through sand in the middle room, collects in the third room, where the clean water drains off into the surrounding soil. This is what I use for my house, and the runoff water keeps them happy during the dry season.
5. One of the programs I saw on environmental solutions on the BBC was for making roofing tiles from recycled plastic bags. Apparently, this technology is used widely in Asia; though I'm not sure how durable these tiles are, they are an alternative to the particle board/ asbestos building materials which are widely used. Here's one link. However, I read one magazine article a while ago which said that the impact on the families making these tiles is quite high - the fumes from the plastic are bad. Plus I imagine that burning plastic releases dioxins which is not good.