RGB2CYMK is a utility program for converting RGB or plaette-color format TIFF files to CYMK format TIFF files.  No, this isn't exactly rocket science, but sometimes you need to do this and your commercial packages won't do it, or won't do it right.  The program will not let you change the gamma, so the color may come out funny.  Different programs will use different gammas, and the result can be images that unexpectedly lose or gain brightness in the mid-tones.

Click here to download the executable, or here to download the executable and the source code.