Cassani is injured ATM. I think it's between him and Maggio for the RB spot at Euro 2012. I reckon Abate should be looked at as well, he's improved big time at Milan this season.
Italy don't have many options at LB though. Only Balzaretti and Criscito. I don't consider Chiellini a LB anymore, and I doubt Prandelli will deploy him there again.