Free .NET Grid Computing software
Digipede Tecnologies has a free Developer Edition for grid computing with free licence for a server and 2 nodes (ie. 2 computers or 2 CPUs running any version of Windows supporting .NET 1.1/2.0)
Read more abour Digipede grid computing from these blogs:
http://powersunfiltered.com/http://westcoastgrid.blogspot.com/http://krgreenlee.blogspot.com/http://et.cairene.net/