Paul Wintour has created a 15 page document that outlines the differences and similarities between some Grasshopper and Dynamo Nodes. If you know one of the programs but not the other, this may be a good place to start…

Download at: Dynamo For Grasshopper users pdf

From Parametric Monkey:

To assist Rhino users in becoming acquainted with Dynamo, I have produced a ‘Dynamo for Grasshopper Users‘ primer. Since everything is a little different in Dynamo, the primer provides a list of ‘translations’ in order to find a comparable node/component.