Gridcoin is a cryptocurrency which securely rewards BOINC computation (volunteer distributed computing projects which attempt to cure diseases, map the milkyway, search for extraterrestrial life, etc) on top of proof of stake.

Anyone can create a BOINC project to create a distributed cloud service of their own desire, Gridcoin rewards a project's volunteers on behalf of the project as opposed to having to pay for computation up front.

If you've got an old computing sitting about gathering dust, you could be helping attempt to cure diseases whilst being reimbursed through the gridcoin network.