A really solid introduction to the passive voice (and another of my successful interview lessons)! Warning: many example sentences are based on recipes for e.g. Lebkuchen/Gluehwein - do not teach this on an empty stomach!
There is enough for two lessons here, or perhaps one lesson and a homework.
First lesson: focus is on UNDERSTANDING the passive voice, in the present tense only. Agents using 'von' are also touched upon. (.ppt and handout 1)
Second lesson: the focus turns now to using the passive in a range of tenses: present, imperfect and perfect. This worksheet provides systematic practice in the style of a real-life situation.