Malaria Control — for stochastic modelling of the clinical epidemiology and natural history of Plasmodium falciparum malaria.
[email protected] — to predict protein structure from protein sequence.
[email protected] — deduces DNA sequence, given a protein.
[email protected] — to predict and design protein structures to fight diseases such as Cancer, Malaria, HIV and Alzheimer.
SIMAP is a database of protein similarities using distributed computing to detect sequence similarities.
TANPAKU — to predict protein structures from DNA sequence.
World Community Grid — advance our knowledge of human disease.
Climateprediction.net — tries to produce a forecast of the climate in the 21st century.
BBC Climate Change Experiment — (part of Climateprediction.net)
Seasonal Attribution Project — (part of Climateprediction.net)
Physics and astronomy :
[email protected] — search for spinning neutron stars (also called pulsars) using data from the LIGO and GEO 600 gravitational wave detectors.
[email protected] — help scientists at CERN to simulate particles travelling in the Large Hadron Collider.
[email protected] — Search for ExtraTerrestrial Intelligence (SETI). The project will host:
Astropulse — searching for primordial black holes, pulsars, and ETI. Originally slated for a 2003 release, some Astropulse work units are only now being distributed. Not all the released workunits are being successfully crunched to completion, but then again, that's the purpose of a beta project: To test, find problems, and correct them. This project is clearly not vaporware. On January 31st 2007 a new beta of the application was released . 
[email protected] — attempt to solve the ABC conjecture problem.
SZTAKI Desktop Grid — searches for generalized binary number systems.