Google Classroom is a new tool in Google Apps for Education that helps teachers create and organize assignments quickly, provide feedback efficiently, and easily communicate with their classes.
Piazza
Piazza is a question-and-answer system designed to streamline class discussion outside of the classroom. It could be used as students' first recourse for seeking answers to their questions about the course, lecture or reading material, or the assignments.
Instructors may use Piazza for dissemination of materials (e.g., homework and lecture slides) and online class discussions. Piazza is a venue to ask questions, discuss problems, and help each other out. If instructors would like to include "participation" as parts of the final grade, Piazza may be a helpful tool to record students' participation for the course. Instructors may also use Piazza for all course announcements.
Prezi is is a presentation tool that can be used as an alternative to traditional slide making programs such as PowerPoint. Instead of slides, Prezi makes use of one large canvas that allows you to pan and zoom to various parts of the canvas and emphasize the ideas presented there. The theory behind Prezi is that our ideas are not linear, but rather bundles of interconnected concepts that are better captured as a whole with many parts. Prezi allows the user to illustrate the relationship of concepts to one another.
These are well known services for hosting videos:
Many students will want to share their videos with other students, but not necessarily make them public to the whole world on the internet. In this case you may find it useful to make your video "unlisted". This means that only people with the link can view the video, so no one would be able to search and find it by accident.
To do this, upload a video to YouTube then in that video's settings, change the privacy from public to unlisted.