The listgeo utility that comes with libgeotiff is a nice command-line utility that can extract the TWF file from GeoTIFF files.
For example, I have a directory of GeoTIFFs, and I have libgeotiff installed as part of OSGeo4w. You can run the OSGeo4w shell, and do this:
c:\dat\NZ-Topo50>listgeo -tfw BN24_GeoTif_1-01.tif
World file written to 'BN24_GeoTif_1-01.tfw'.
It would be nice if the same utility could also extract the PRJ file too.