Normally, when you empty your computer's trash or recycle bin, files are (mostly) removed from your computer. A new open-source project called Dumpster Drive is hoping to turn that on its head. To get Dumpster Drive to work, you install client software (which is at this point Mac-only, though they're hoping for others to port it to Windows and Linux) which adds a Dumpster folder to your desktop. You drag any unneeded files to that folder, and then use the client software to empty the dumpster folder.
The files are deleted from your hard drive as normal, but are then uploaded to a Dumpster Drive server, which anyone else with the client software can access and download files from. There's a catch: the files left on the central server can only be downloaded once, though it's possible to replace them once you're finished.
It's a novel idea, but I have some concerns. Dumpster Drive doesn't have a policy towards copyrighted material, so although I'm no lawyer, I can see how it may end up in legal hot water. There also doesn't seem to be any sort of security systems in place to restrict the spread of malware through Dumpster Drive, and anything you share on it can bee seen by anyone else. Indiscriminately deleting personal documents via Dumpster Drive would be a bad idea.
At the same time, if you need to clean out your collection of lolcats, why not share them with someone else?
Mac users can download the Dumpster Drive client from the Dumpster Drive Website. If you're not on a Mac, but want to give it a shot, the source code is available from the project's github repository, and able to be freely modified.