123D Circuits – Design, compile, and simulate your project online

http://www.123dapp.com/circuits

With 123D Circuits you can design in a familiar breadboard view and the app will guide you to make professional printed circuit boards with built in layout tools. When you’re done just click to have your boards professionally manufactured and shipped for free worldwide.

What’s also cool is how you can easily, simultaneously work on the same circuit with your friends. And at any point you can compile and emulate your Arduino code inside a live, editable circuit!

Installing an Arduino Bootloader

https://learn.sparkfun.com/tutorials/installing-an-arduino-bootloader

Here is the description of this series of Web pages. I bolded the part that was of interest to me !

Do you have a bricked Arduino that won’t accept code anymore? Or, maybe you wrote your own firmware and would like to upload it to your Arduino? Or, maybe you just want to learn more about the inner-workings of Arduino, AVR, and microcontrollers in general. Well, you’re in luck! This tutorial will teach you what a bootloader is, why you would need to install/reinstall it, and go over the process of doing so.