FMACJ is a parallelization framework for the .NET CLR that gives your applications multicore/cluster support by saying what should be parallelized via attributes. You do not have to think about threads and networks at all. FMACJ also runs on Mono.
NGrid is a transparent C# .Net/mono grid computing model. NGrid abstracts the burden of the grid into a simple multithread and garbage collected programming model. NGrid is designed to carry computationally intensive tasks over multiple machines.