Primecoin is designed to search for prime numbers, which is at least somewhat useful. Ripple Labs is giving away Ripple (XRP) for donating your computing power

Primecoin is designed to search for prime numbers, which is at least somewhat useful. Ripple Labs is giving away Ripple (XRP) for donating your computing power to solving scientific problems at https://www.computingforgood.org/ https://www.computingforgood.org/.