I developed a workflow solution 'Connect-Share-Do' which is intended to support multi-domain processes for small to large businesses and teams. It has some users but I am still looking for 'early adapters'. For new customers I offer free implementation and support now. So, if interested, please give send me an email firstname.lastname@example.org or call me at +31(0)610 865 896.
You can build your own workflow enigine. I good place to start reading if you want to create your own is http://www.workflowpatterns.com/
I have builded a workflow engine this way in a couple of days that has been handling all our workflows for the last two years now.
Problem with most workflow engines is that it is very hard to make it appstore ready. In our case we have one mutation object that flows through the workflow engine. And that object is offcourse different for every workflow sollution.