A good way to search for and see reviews for apps. This will search apps based on several criteria that you can set like grade level, subject and level of interactivity.
A site where you can create, manage and control blogs for students. You can create an environment where students can blog and it is only seen by people that you give access to.
A way to have visual discussions in class. Students can make comments from their laptops and they can collaborate in a small group setting or show through your projector for whole class discussion.