I hand these cards out at convention panels & workshops along with a couple LEDs and a coin cell all in a 3×4″ Ziplock-style bag. There’s three double-sided cards: one for electronics principles, one for Arduino, and one with some terminology and eye-catching photos. Though designed for beginners, I’ve had a few pros ask for spares too! (The resistor color codes seem especially popular.)
Adobe Illustrator format. These are sized for Overnight Prints‘ standard business card template; full color, double-sided…rounded corners are optional but add a touch of class (and won’t cut off any information). Creative Commons license, feel free to print your own, remix and share!