If your subject involves creating flow charts, venn diagrams or thought showers... previously known as brainstorms, then your should try Lucidchart. Using your Google Drive account a number of people can collaborate on a chart in Lucidchart.
The app will appear on your Google Drive. You can click on create and off you go. To give you more information, there is a video below from Lucidchart.
Currently we have a trial. Let me know if you like what this app has to offer your classes.
If you know of or use any other websites or apps that can integrate into our Google Apps for Education account please let me know.
Mr B Rouse