SwapChain is a browser extension that encourages people swap your time on certain sites (e.g. Twitter, Reddit, Facebook, etc. etc.) to do something more valuable instead. The power budget saved by this action is then offered up for others to use for a valuable blockchain application. Your own CPU can be donated towards this if you want.
In this way, useful blockchains can be run in a more environmentally friendly way, while at the same time giving people an incentive to wean themselves off time wasting and harmful online activities.