Indiana University Extreme Computing Lab - Outdated but still interesting
NCSA Grid Computing
Open Grid Forum - Talk with other distributed computing types
Grid Computing Info Center
Internet2 & Grids - I know... where is Internet2 for everyone?
GRID - Community for OpenSource grid computing
GridWay OpenSource
The Kepler Project
The Sakai Project
The GridLab
Data Mining Grid
IBM Grid Computing - Big Blue in the grid
Oracle Grid Computing - Big databases need big processing
Oracle Achitect Center - Designing the grid and the apps for the grid
Grid Computing Planet - Latest News on Grid technology
World Community Grid - Supercomputing to help humanity
SunMicrosystems Grid Engine - Sun's java-powered griding
JavaWorld Java Framework - Great little article on creating your own framework for distributed computing.
Globus Alliance - Another grid group
BOINC - Berkeley Open Infrastructure for Network Computing