Social media can actually be useful for more than sharing pictures of your lunch! There is a whole collection of apps and web services that can be used to help development efforts around the world. They provide the ability to track how projects are coming along and their current status to being able to connect farmers to more information and their own local social networks.
My favourite service is one that allows people to report corruption:
I Paid a Bribe is an anticorruption movement that harnesses the power of collective voices. Protected by anonymity, users are encouraged to report on corrupt acts, through a website, email or SMS. The reports are mapped on the site and used to inform campaigns for better governance. The movement is active in India, Greece, Kenya, Pakistan and Zimbabwe, after its founder, Tawanda Kembo, was pressured to pay a bribe by a corrupt police officer, and will be coming soon to the Philippines and Mongolia.