Updates 8-25-15 (New post button, bumping old posts, reusing old posts, and adding questions)

Google Classroom Overview

Classroom Updates - April 2015
Google updated Classroom with some key features today.  You now have the ability to add co-teachers, who can do everything but delete the class, by going to the About page and clicking the Invite button.
You can also save Announcements or Assignments posts until later.  Create it now as a draft and then submit it when you want to.  This allows you to easily plan ahead without students being able to see it ahead of time or work on it.  Just click on the down arrow next to Post.
You can also apparently save grades without returning the documents and email notifications were improved.  You can find more about the updates by going to Google's own post about them, http://googleforeducation.blogspot.com/2015/04/teaching-teams-new-ways-to-work.html.
Add to Classroom Chrome Extension

Student Introduction to Classroom

Turning In Assignments (for Students)