eBM WebSourcing Developers have just released a new Eclipse plugin (v0.9.0 with EPL License) which allows to create Service Units for some PEtALS components (SOAP, File transfer, EIP, XSLT) and package them into Service Assembly in one click.
The installation guide is available at http://forge.ebmwebsourcing.com/petals-eclipse/ and the project is hosted on the eBM WebSourcing forge at http://forge.ebmwebsourcing.com/
I have also created a topic for this plugin on the forum at http://www.ebmwebsourcing.com/forum/viewtopic.php?t=30