The process of writing large parallel programs is complicated by the need to specify both the parallel behaviour of the program and the algorithm that is to be used to compute its result.
Lambdabot is a Haskell development tool, written in Haskell. It operates as a command line tool, embedded in an editor, embedded in GHCi, via internet relay chat and on the web. More information is available at the Haskell wiki.
If you read discussions about programming languages, one topic is quite common: "Why do people use an inferior language like Java/C++/what-the-hell and not a superior language like Lisp/Haskell/Python/you-name-it"?