As a software developer if the necessities, project steps are well documented, I can design and develop the new projects in time, maybe in a shorter time. Else whole the workflow is done by the developer. He/she creates the cycle of the workflow of project in his/her mind and starts developing according to that thought or the workflow he/she hears from the manager.
Today I got a newsletter from Adobe Edge. Sometimes I am bored on these kind of periodic mails. But Adobe's mails interest me and I read them (I receive them monthly). At the ends of the mail there was a link to a new project which is a workflow engine project that excited me. It is named as "WorkflowLab". By this application you can design the steps of a project using a user friendly graphical user interface. And creating a task you can define your applications that you will use in this step. This is a good property of the program. But whole the defined programs are Adobe's tools. I could not see an "other" choice and could not define custom tool. But I saw that next year they will provide this capability.
I used several workflow tools and developed a workflow tool for a company during my internship. None of them was fast as this program and none of them uses low disk space. You can find an install the program from http://labs.adobe.com/technologies/workflowlab/ and you can find detailed information from http://www.adobe.com/newsletters/edge/october2009/articles/article5/index.html?trackingid=EXBIG . If you are looking for discussions and forum you can use http://forums.adobe.com/community/labs/workflowlab/.
By the way, the program is lightweighted and uses 2MB of disk space. The program is free of charge.