Lino it is an easy to use webapp that lets you post and share stickies for a project, class discussion or brainstorming session. You can log in via the web, or use a dedicated iOS or Android app to access your board.
This short vimeo clip shows how to use the features. I think you could easily use "groups" for classroom notetaking. (See another clip below.)
There's also helpful "how to" lino board.