I recently had use for the simple signal generator. I described before for testing out some piezo buzzers I got for next to nothing. I reloaded the code onto a TAP-28 board I had handy, made the connections and was quickly rewarded with some noise.
Since I find this really useful to have around, I decided to dedicate a TAP-28 board to the task and mounted it in an enclosure. The the same time, I wrote a simple Windows (sorry Linux guys) application to control the signal generator. No more button pressing and terminal emulator. Just enter the desired frequency and duty cycle and away it goes. Very handy.
The full details including a schematic diagram, Swordfish Basic source and compiled files and the Windows application can be found on the ThrowAwayPIC site.