@cazzie – Yes, there were several. And the most elaborate one was headed by Stauffenberg, see http://en.wikipedia.org/wiki/Stauffenberg_assassination_plot
A more detailed description about German resistance including the prewar period can be found here: http://en.wikipedia.org/wiki/German_Resistance
My personal heroine is http://en.wikipedia.org/wiki/Sophie_Scholl – she was a student in Munich, distributing leaflets with content like:
“Isn’t it true that every honest German is ashamed of his government these days? Who among us has any conception of the dimensions of shame that will befall us and our children when one day the veil has fallen from our eyes and the most horrible of crimes—crimes that infinitely outdistance every human measure—reach the light of day?”
“Why do you allow these men who are in power to rob you step by step, openly and in secret, of one domain of your rights after another, until one day nothing, nothing at all will be left but a mechanized state system presided over by criminals and drunks? Is your spirit already so crushed by abuse that you forget it is your right – or rather, your moral duty – to eliminate this system?”
“Since the conquest of Poland three hundred thousand Jews have been murdered in this country in the most bestial way … The German people slumber on in their dull, stupid sleep and encourage these fascist criminals … Each man wants to be exonerated of a guilt of this kind, each one continues on his way with the most placid, the calmest conscience. But he cannot be exonerated; he is guilty, guilty, guilty!”