There are so many great places online to learn about circuits and Arduino already, we’re going to link to them rather than repeat it all here.
YouTube – Collin’s Lab – Collin Cunningham’s excellent series of videos explaining everything from the basics to advanced topics. These videos are short, entertaining, and many of them are easy to understand for beginners. Be sure to scroll to the bottom of the list to start from the beginning.
Here are some of our favorites:
Adafruit – Adafruit is a NYC-based company that is a fixture in the maker community. They sell just about everything (much of which they’ve created) and have tutorials for the things they sell.
Sparkfun – Sparkfun is a great place to buy electronics and learn how to use them.