Node Pie is a Blender addon that converts the usual blender add node menu into a pie menu:
Node.Pie.demo_optimised.mp4
As well as that, the size of the buttons will change depending on how frequently you use each node; nodes you use a lot will have larger buttons, and nodes you don't use much will have smaller buttons:
It also works in all Blender Node editors, and even in custom node editors created by python addons:
You can install Node Pie by downloading this repostory as a zip file, and then installing it like any other addon.