Yes, it´s Shift-A, which does not really make sense for such an important menu. But it can be easily changed from the user preferences, since the right click is not assigned to any function there anyway. – If you use left click select that is, I guess.
Edit, the pie menu addon I mentioned earlier does not seem to offer the most common shaders like Matte and Glossy unfortunately. – I guess I will continue to use the sidebar for now. 