Really liking the idea behind this application by Justin Blinder.

Dumpster Drive: File Sharing For Your Digital Trash from Justin Blinder on Vimeo.

Dumpster Drive is a file-sharing application that recycles digital files. Using dumpster diving as a model for recirculating unwanted objects, Dumpster Drive allows others to dig through files that you delete on your computer in a passive file-sharing network. Instead of simply erasing data from your computer, the software allows users to extend the lifecycle of their unwanted files and pass them on to others.