Digital trainers integrate a breadboard with simple I/O and they are a great tool to learn digital circuits. DIGILAB-R is a vintage style digital trainer designed to be compatible with the Scuola Radio Elettra DIGILAB. It can be used to perform all the experiments in the Digital Electronics distance learning course that was popular in the 80's.
Many MCU applications use electro-mechanical relays to control AC loads. While this is an excellent solution for occasionally turning on/off a load, it is not suited for frequent switching or PWM applications. SSR1/A is an opto-coupled solid state relay that can control two AC loads in a arduino shield form factor.
While working with Arduino in industrial applications it's often useful to have a isolated voltages available. Depending on the circuit configuration, ISO02 can generate galvanically isolated unipolar and symmetric voltages from the 5V Arduino power. The circuit is based on a basic push pull configuration and uses an easy to obtain off the shelf transformer.