Make a set of index cards with phrases that can be said in the passive or active voice (e.g., "The dog ate the food" versus "the food had been eaten by the dog.") Give kids a monopoly board and two dice. After they roll the dice, give them a card and tell them to say the phrase in the passive voice. If they do so, correctly, they can move ahead on the board. If not, correct them.
Make a set of game cards with verbs on them ("stepped on," "bitten by," "prevailed over," for instance). Make another set of cards with pictures of body parts, and yet another set with pictures of insects, animals, and people. Put your students in groups of three, and give each group a card from each set. Have them put the cards together, in the passive voice, in a way that makes sense.
Make a set of flashcards, with different categories. One category might contain pictures of household appliances, another might contain images of famous people, and a third might include photos of items found in nature. Be creative! Put your students in pairs, and have them take turns playing. When a student has a card, he should tell the other what category his card falls into. The other student, in turn, should ask him questions about the card, in an attempt to figure out what the card is. When the student responds in a complete sentence (e.g, "It is blue," "It is used for cooking,") he will get practice using the passive voice.
Make a set of playing cards, that contain phrases written in the active voice. Put your students in pairs, and distribute the cards evenly among the pairs. Students should play war with their cards, putting the phrases on the cards into the passive voice. If one student in the pair uses the passive voice incorrectly, then the other student takes both cards. If both use the passive voice correctly or incorrectly, then they should keep their respective cards. Give the students several minutes to play!