Engineering for Change is an online environment bringing together engineers and other problem solvers with NGOs and local communities to address basic quality of life issues such as access to clean water, electricity and proper sanitation. Also see their Twitter feed
Related:
+ Engineers Without Borders
+ Architecture4Humanity
+ Open Architecture Network
+ Entrepreneurial Design for Extreme Affordability
+ D-Lab @ MIT
+ Wisdom from Paul Polak on How to Design for the Market