OK, how about a processor-controlled design where the processor is a single 8-pin chip, like the PIC12F675? You use the internal clock, so eliminate the crystal or resonator. Use a single ADC pin to read a 20-switch keypad designed to work as a simple voltage-divider design. Use a serial-LCD for a display, thus using a single output pin versus the usual seven or so for a typical four-bit LCD. Use a single pin to both read a switch (input) and drive an LED (output). Use an IR transciever to communicate with the outside world, and eliminate all the large connectors typically employed to connect cables to. Use a 5V, 20 mA relay to turn a small AC device on and off. All this leads to smaller, less expensive boards which take up less landfill space at the end of their useful life. Microchip has an app note with handy little suggestions like that.
Do a cost study of SMT versus through hole for the board. Is there any real savings in eliminating plated-through pads? What are the considerations of doing a single-sided board versus a double-sided one?
Pick a simple a simple household device, like a Mr Coffee coffee maker, with clock readout and programmable brew starting, and design for "sustainable engineering".
And have fun doing it.
kenjj