Gridcomputing - http://www.gridcomputing.com - The Grid Computing Technology Infoware (GRID Infoware: http://www.gridcomputing.com) aims to contribute to the development and advancement of technologies that enable us to access computing power and resources with the ease similar to electrical power
distributed.net - http://www.distributed.net - A distributed computing project currently trying to take the RSA challenge of RC5-64, and also working on OGR-24 (Optimal Golomb Rulers).
The Globus Toolkit - http://www.globus.org - The Globus Toolkit provides software tools that make it easier to build computational grids and grid-based applications.