BSPlib is a library for Bulk Syncronous Parallel (BSP) Programming.
Epeios is a set of C++ libraries which include a new concept of memory management and error handling.
Hoard is a fast, Scalable, and Memory-Efficient Allocator for Shared-Memory Multiprocessors.
a 2-layer abstraction library which simplifies the usage of shared memory between forked (and this way strongly related) processes under Unix platforms
provides an easy way to program the widely used parallel programming library PVM, which works in homogenous and heterogenous network environments
pvmsync is a distributed operating system which provides synchronization mechanisms (mutexes, semaphores, and condition variables) and shared data (integer, floating point, and a raw block of memory) to processes distributed throughout a beowulf cluster.