Great recommendation from Toby, extremely interesting concept following on from the investigation of helpful, useful, ethical apps.
Left Over Swap app connects those who have left over food to those who are peckish! There is a very interesting TED video from the founder Tristram Stuart: http://leftoverswap.com/benefits.html
I tried the app last night, there was a meal ready for me to pick up in Oxford. Heheheh! Love the concept though. Waste not want not.