Hey Chuck -
If memory serves, you used to play the slot machines in a certain area of the casino. The machines were connected to a ticket machine similar to the type of arcade tickets that you get for playing skeeball.

As you play and push credits through the machine the ticket machine will spit out tickets, then hit a certain amount and you get one.

They have a similar promotion for other prizes now, as well as a "trip in the fortunedome" which is basically a sphere that has a fan underneath blowing money around and you have to catch it. Of course in AC style they went from allowing you to grab it to basically letting you stand there with a net and whatever falls in is yours.