There were several spies in the german command structure (the german counter-espionage division Abwehr might or might not have been doing a rather bad job on purpose) and there was the Weiße Rose resistance group. There were also lots of secret acts of resistance/support for jews etc. by ordinary people. There were 42 attacks on Hitler's life.

That's not nearly at the level as e.g. the highly organized french and belgian Résistance, though.