Ben Long has expanded his Photoshop Action Pack with a new Automator action for DNG Conversion. To use it you’ll need the free DNG Converter for Mac. [Update: Thanks to Geoff Stearns for pointing out this DNG Workflow resource that ties the converter together with a folder action and a rename function.]
That’s excellent… If anyone else is interested in more DNG workflow tips, there is a great post here about a very nice setup: http://www.protozoic.com/2005/11/08/dng-workflow/