Anyone who deals with circuit simulation or is interested in it can find a graphical interface for Spice under the link, which allows you to operate the package in a somewhat more Mac-typical way. Spice is one of the most sophisticated systems for circuit simulation (so transistors, resistors, inductors and that sort of thing). Might be quite interesting for electronics hobbyists (for me it's not, I'm too stupid to hold a soldering iron the right way around).