Flubaroo is a script that you can add on to your google spreadsheet/google form which will automatically grade quizzes, and even send an email with the grade (and even answer key) to your students.
It is easy to use. Just create a form. Fill it out with the correct answers to make the answer key. And then run the script.
This video shows how to use the Flubaroo script. I also demonstrate how to add an image into a google form and how to search for Creative Commons images. (Creative commons images are liscensed by the owner for to be allowed for public use if they are given attribution. Find out more at creativecommons.org)
Here is a sample quiz, it is the one I made in the video: