Batch photo manipulation via free software tools?

I have a need for batch-processing pictures. My requirements are fairly simple:

• Resize the image to fit Facebook's preferred 960 pixel box.
• Insert Copyright, Byline and Bylinetitle into the EXIF data.
• Optionally, paste my watermark onto a predefined corner of the image.
• Optionally, adjust the white balance.
• Rename the file according to a specific syntax.
• Save the result to a predefined folder.

Until recently, I was using Phatch to perform all of this. Unfortunately, it cannot edit the EXIF data of my current Lumix camera, whose JPEG it claims to be MPO. I am thus forced to look for other options. Ideally, I would do this via a script inside gThumb (which is my main photo editing software), but I cannot seem to find adequate documentation on how to achieve this.

I am thus very interested in hearing about other options to achieve the same result. Ideas, anyone?

Batch-editing EXIF data to add copyrights?

I've recently become more serious about my photographic hobby and it dawned onto me that manually editing each JPEG to add my copyright was entirely the wrong approach. Thus, I was wondering if anybody would know of a Free Software tool that can batch edit the EXIF data in JPEG images? What I'd like to accomplish is simple:

• Add the string Copyright ©$YEAR Martin-Éric Racine where $YEAR is directly extracted from the original EXIF data's day when the picture was taken.
• Optionally, produce smaller versions of the source images to an output folder as TFCD samples for my models to take home.

Preferences go for a tool that is already packaged for Debian or Ubuntu but, worst comes, I could package the software myself.