A lot of sabotage was made using DIY bombs cooked from fertiliser in people's kitchens. Good old-fashioned arson was also easy to do when you didn't have access to explosives. Later on in the war the allies (at least the British) began air dropping guns and explosives to the resistance movements in occupied Europe. For many resistance fighters receiving and storing these deliveries were their main contribution to the cause. As the war kept going and the resistance became better organised clandestine factories around occupied Europe began producing simple weapons like Sten guns.