GitHub repository: yahoo/FlowEtl
Primary language: Java
Description: This is a framework designed for the creation of testable components which can be interconnected via arbitrary inputs and outputs and those components can be executed in the correct order (inputs satisfied before running) automatically. This is useful since it aids developers in thinking in the paradigm where they plan components ahead of time, allowing for simpler reuse and refactoring later. At yahoo! this was created for a ETL like framework & pipeline, but its applications are not  limited to solely that, since the concept itself is generic.