10. Chapel

Chapel is part of Cray's Cascade Program, an ambitious high-performance computing initiative funded in part by the U.S. Defense Advanced Research Project Agency (DARPA).Designed keeping supercomputing and clustering in mind, its goals are abstracting parallel algorithms from the underlying hardware, improving their performance on architectures, and making parallel programs more portable.

Chapel draws its syntax from numerous sources like C, C++, Java, Fortran and Matlab. Its parallel processing features are influenced by ZPL and High-Performance Fortran, as well as earlier Cray projects.

It also supports "multi resolution programming," which allows developers to prototype applications with highly abstract code and fill in details as the implementation becomes more fully defined.

At present, it can run on Cray supercomputers and various high-performance clusters, but it's portable to most Unix-style systems (including Mac OS X and Windows with Cygwin). The source code is available under a BSD-style open source license.