Weird that nobody mentioned spreadsheets until now... spreadsheets are one of the possible data flow implementations.

Probably few people know but Microsoft Excel has some optimizations like "multithreaded recalculation" http://msdn.microsoft.com/en-us/library/office/bb687899.aspx and "high-performance Excel based applications in financial services" http://msdn.microsoft.com/en-us/library/bb887539.aspx

I included extra resources at the end of my articles on the subject: http://blog.databigbang.com/category/egont/