A fellow Google +er posted about Real Time Board a few days ago. I checked it out and was impressed with what I saw. It is a White Board + app that links with your Google Drive.
The education account limits you to 10 boards but the app does not appear to have other limitations. If you plan on using it for work just make sure you log on with your district email account. The advantage to this is all your work in Real Time Board can be saved in Google Drive.
While there are several White Board apps out there, the advantage to Real Time Board is Google Drive integration. The little bit of time I messed around with it the more impressed I was. The tools are basic enough I could see myself using this tool for a lesson with students.
Don't take my word for it, watch the screencast and decide for yourself.