If you have the Royal Road, I know there is a Routine in there where the spectators stand up and close their eyes. You name 3 cards and if their card is named they sit down. When they open their eyes, they are all sitting down. You can use a prop like Akkeline Envelopes to do a mind reading routine with multiple people.
If you have Daniel Madison's Advocate, you could perform "The Invisible Card" with multiple people. In fact, I am practicing this one right now.