f/Calc is a utility to calculate lens formulae for photographers so you can focus on the artistic bits rather than on the mathematics behind it all. f/Calc can do "f" number arithmetic, and can calculate depth of field, hyperfocal distance, the field of view of a lens, the angle of view of a lens, magnification, and how the focal length of the lens on the camera changes the way the spot metering function works. In addition to the Unix/Linux Tcl/Tk version, there are native Windows, Palm OS, and Macintosh versions as well.
The par utility creates and manipulates PalmOS database (.pdb) and resource (.prc) files. Par is designed to be a Swiss army knife for managing these files. It's a command line tool, and not for the faint of heart, but it's very handy and replaces a bunch of little utilities that you might otherwise use.