I recently hosted a couple of Austrian couchsurfers. It was great exploring Melbourne again through the eyes of a tourist. Turns out, the highlight for them was Lentil As Anything. They had never experienced anything like it, and I must admit, it is one of my favourite places.
You help yourself to delicious food.
Chat with the familiar staff and patrons.
Leave a message on the wall (or browse those already there).
And then simply leave your money in the box.