From solar lamps to Kindle readers, the transformative power of affordable new technology is the theme of Future Africa - this year's Guardian and Observer Christmas appeal. The projects being supported demonstrate how simple, positive technological interventions can create momentous, positive change. Charity beneficiaries are Practical Action, Worldreader, SolarAid, and Farm Africa. The Guardian is also continuing to support Katine, the African village it has supported since 2007.