First, the list of everything I use in my workflow:
Additionally I use F-Spot for importing, file management, and quick viewing. Right clicking on the photo can open in GIMP or UFRAW
For the command line:
Metadata: Exiftool by Phil Harvey
You can do a lot with ImageMagick
Here are some of the scripts and plug-ins I am using. Details and reviews of which will come over time.