For truly sustainable change, our technology needs to not only provide a solution, but it needs to be appropriate - appropriate to the environmental, economic, and cultural situation. Appropriate technology tends to be simple technologies which are suitable for use in developing nations or in less developed rural areas. For instance, photovoltaic panels and large battery banks don't make much sense for areas without the means to purchase or maintain them.
The absolute best resource that I've found for appropriate technology is Appropedia, an appropriate technology wiki with user generated and edited content. Do it yourself-ers, people looking for ways to help others help themselves, and anyone working for positive change in the world will find something to use and to share at Appropedia.
"Our vision is that all of humanity is able to work together developing and realizing rich, sustainable lives. We build the infrastructure, and help make the connections and populate free content to effect that vision. We provide the living resource library of individuals and organizations working towards a sustainable, healthier future, so that efforts can be spent evolving instead of duplicating past efforts.
Sharing knowledge to build rich, sustainable lives."
Appropedia provides a wealth of information on appropriate technology to use and share. I recommend bookmarking it for reference, and if you have anything to add, sign up as a user to help grow this incredible resource. You can help make the world a more sustainable place, right from your keyboard.