The World Community Grid is one of the early cloud computing efforts helping calculate science projects mostly in health research but also areas like clean water. I've been one of the volunteers for a little over a decade.

Basically, what happens is a small math problem is downloaded to your computer and the program uses idle cycles to do the calculations and then return the results. Your results are then compared with at least three other folk doing the same calculations to check for accuracy.

So far I've been able to contribute the equivalent of over 40 years in run time while never even noticing that the program is running in the background.

This is a way to provide research help at no cost to you that may well help end some of our current scourges.