@duglop Have also seen this done via a community blackboard wall where people write (and pay) amounts. They either leave their initials or stay anonymous. I like that because it builds a gestalt of giving.

In my very favorite place to eat out the Host is empowered to take anyone to a table, bring out a meal and not a ticket. I think the owner subsidizes those. Seems to work for them; completely invisible to patrons which has plusses and minuses.