A few months ago I stumbled across an interesting usage of blockchain technology: golem.network .
To put it simply, it allows you to rent our your computer to do work for other people in a safe and decentralized way. This means that desktop computer you have running all day doing nothing can now at least be making you some money to offset the electricity bill.
At first I started as a provider - renting out my computer. It won't make you rich, but when the network is active it's definitely enough to offset electricity costs - and then some.
It's still in the Alpha phase, but it is able to do real work. Their "go to" example is that it can render 3D animations with Blender. But really, it can run gWASM natively, or it can run anything that is Dockerized.
As a proof of concept I built a Docker container that allows you to use the golem network to perform calculations with the OR-Tools library.
Then, they opened up bounties! I built this video transcoder over a weekend:
It's a very rough proof-of-concept, but it lets you upload a video, sends it to the golem network to process, and then returns the transcoded video back to you. Is it world-changing? No, but it does show that you can offload CPU-intensive tasks to other people's computers (or yours) for a low price without contracts or account sign-ups.
So far, I'm quite happy with it and I look forward to the New Golem release!