Wok
Wok is a workflow management system implemented in Python that makes very easy to structure the workflows, parallelize their execution and monitor its progress. It is designed in a modular way and can be adapted easily to different infraestructures.
Currently it is focused on clusters implementing a DRMAA interface (such as the Sun Grid Engine) that share a folder between the execution nodes. Other, more flexible infrastructures (such as the cloud) are being studied for future implementations.
The source code is available at the Bitbucket site