Another nice project done by/at my former CS research group (by one of my ex-colleagues, Cesare Pautasso): JOpera, a process engine for web services.
This technology could be used to build a BPEL engine or any other type of workflow engine for service-oriented architectures.
I wonder if they need transaction support — if so I know where to get it 
I also think BPEL and its compensation model have serious flaws, maybe this tool can offer something better.