PTtiff2psd is a utility to convert a set of TIFF files into a multi-layer PSD file suitable for opening in Photoshop or the Gimp. It was written by Daniel M German. A multi-platform version is now included with the pano12 library available at Sourceforge.
The functionality is similar to Erik Krause's Photoshop stitching actions, except PTtiff2psd is a standalone command-line program.
Usage is like so:
PTtiff2psd [options] <tiffFiles>+ Options: -o <filename> Output filename (default merged.psd) -m Add stitching mask -r Reverse layers