If you've got Nvidia you can crunch:
GPUgrid: Full-atom molecular simulations of proteins
Asteroids@home: Asteroid research - it uses photometric measurements of asteroids observed by professional big all-sky surveys as well as 'backyard' astronomers. The data is processed using the lightcurve inversion method and a 3D shape model of an asteroid together with the rotation period and the direction of the spin axis are derived.
If you've got AMD you can crunch:
Milkyway@home: Creation of a 3d map of the milkyway galaxy using data gathered by the Sloan Digital Sky Survey. This project enables research in both astroinformatics and computer science.
POEM@HOME: Models protein folding using Anfinsen's dogma
There's also some multi-gpu compatible projects:
Collatz Conjecture: Attempting to disprove the Collatz Conjecture
Einstein@home: Search for spinning neutron (pulsars) stars using data from the LIGO gravitational-wave detectors, the Arecibo radio telescope, and the Fermi gamma-ray satellite
PrimeGrid: Search for prime numbers. Primes play a central role in the cryptographic systems which are used for computer security. Through the study of prime numbers it can be shown whether current security schemes are sufficiently secure.
SETI@home: Search for Extraterrestrial Intelligence (SETI)
Probably because Gridcoin is an absolute nightmare to setup, the wallet takes hours to days to sync and the money you make is rarely even enough to pay for electricity.
Not saying it's not a lofty idea, but most people here aren't going to jump through those hoops to lose money or barely break even. I love the idea of Gridcoin, but in its current state? Not so much.