Request: Hands-on activity ideas for large groups of people?

I’m hosting a weekly “hands on” activity night and looking for some ideas (preferably cheapish) for 50-100 people. I have in mind to do postcards to voters, but looking for other ideas that would engage people. Has to be hands-on and has to be available all in one building (so no going out to plant trees, for example).

Any way to give back to the community!