Xgrid: High Performance Computing for the Rest of Us: Apple's quick setup grid, in use at many academic institutions.  Released Jan 2004.  A Feb 2004 presentation has good examples from U Utah, including a PDF with rendered images.  Controller and client run only on OS X today; agents can be OS X or Linux.  A Stanford project is looking for volunteers to contribute time for chemistry research.

Cringely points out how cheap fast computing is getting. "Imagine a Mac Minicluster running Apple's xGrid software. Start with a 16-port fast Ethernet switch and stack 16 Mac Minis on top. That's a 720 gigaflop micro-supercomputer that costs less than $9,000, can fit on a bookshelf, and can be up and running in as little time as it takes to connect the network cables. High schools will be sequencing genes."

  9:49:36 AM    

BEEP framework for building application protocols: Well written FAQ, technical intro and examples (like a reliable syslog protocol).  Used in the xGrid system that runs on OS X.  9:34:48 AM