This is a web tool I have already reviewed in an earlier post here in this blog. Real Time Board allows users to collaboratively create brainstorming sessions where they get to share text, pictures, and drawings using links. There is also a chat functionality embedded in Real Board that enables users to chat with each other while brainstorming.
2- Lucid Chart
This is another awesome web tool that students can use for collaborative brainstorming. Its drag and drop interface is pretty basic. Lucid Chart provides you with a variety of canvasses in which you can create different flow charts, mind maps, and organizational charts.
3- Spider Scribe
SpiderScribe is an online mind mapping and brainstorming tool. It lets you organize your ideas by connecting notes, files, calendar events, etc. in free-form maps. You can collaborate and share those maps online