As we rapidly approach one million registered volunteers (awesome!), Rob has produced this lovely plot showing how those users are distributed across the Zooniverse projects. The size of the circle corresponds to the number of registered volunteers involved in the project to date. This includes everyone who has registered for a Zooniverse project since way back in July 2007 when Galaxy Zoo launched, so these circles would look very different if you just plotted them for the last year, for example.