Jug is a task-based parallelism framework. Jug allows you to write code that is broken up into tasks and run different tasks on different processors. It uses the filesystem to communicate between processes and works correctly over NFS, so you can coordinate processes on different machines. Jug is a pure Python implementation and should work on any platform that can run Python.
Plasma implements the map/reduce framework on a compute cluster. It has its own distributed filesystem, PlasmaFS, which is transactional (ACID), reliable, and fast, and which provides a complete set of file operations. PlasmaFS can be accessed via an RPC protocol or via NFS (i.e., it is mountable). Additionally, there is a key/value database on top of PlasmaFS.
MapReduce-BitDew is an implementation of the MapReduce programming model proposed by Google for Internet Desktop Grids. Using MapReduce-BitDew, you can execute MapReduce applications on resources like Desktop PCs distributed on the Internet. MapReduce-BitDew features a firewall-friendly protocol, fault-tolerance, result-certification, 2-level schedulers, and more.