UPDATE: psdlayerstga has been renamed to psdslayer with addition of saving the layers as png files. Get the new tool from here.
I took DrPetter’s PSDImage code for extracting layers from PSD images, and combined it with stb_image just for saving out the layers easily as TGA files. And then I included some simple options and output of the metadata (i.e. name and position of each layer). Result is a little command-line utility, “psdlayerstga”. Use it for anything, but do so at your own risk. (The PSDImage code uses that same license, and stb_image is public domain.)
Download here, including C/C++ source and a pre-built executable for windows:
psdlayerstga.zip
Go get newer version (psdslayer) from here.
Edit: Don’t miss psdparse below (suggested by Toby), an alternative tool for the same task.