Use LED matrices with Arduino!  Build an LED matrix circuit, and then learn how to transform code to  make letters, shapes, and messages on them. 

Use this diagram to learn how to wire an LED matrix so that you can use it in your projects.LED Matrix circuit diagram

Using the code below will produce the letter “M” on your LED Matrix. Once you have that working, see if you can alter the code to create other letters of designs. 
Mastered LED matrics with Arduino?  Learn how to build some other Arduino circuits with these tutorials.