For my track car project I wanted to have a wideband O2 sensor, this in combination with a programmable ECU would enable me to tune the engine myself, and open the road to adding horsepower by forced induction.
After some research, I bought the 14.7 SLC Free kit plus a Bosch LSU wideband O2 sensor. Assembling the kit was a breeze, the component values were both marked on the PCB itself and in the very well written instruction manual. All the parts were through hole, so even a relative beginner could assemble this kit. The only gripe I had was with the tiny pads around some the holes, most likely due to the default settings of EAGLE.
After assembling the kit, it still needed something to protect it from the outside world and to mount it in the car, so I designed a small box to house the PCB and used the laser cutter to turn design into reality.