Recently getting into job looking mode has led me to brush off the Automator routines for combining PDF documents into one document. Unfortunately it doesn't seem to be working in OS X 10.5 (or 10.5.1). A Apple Discussion Forum post suggests I'm not the only one encountering the problem.
When you run the action in Automator it works like a charm. When running the action as a plug-in in the Finder the action swirls for a moment and then nothing happens. From my testing it does not seem to matter what is done with the output of "Combine PDF Pages" nothing happens from there on.