According to the latest Dunkin' Donuts advertising, you can go in between 3pm - 6pm and get any size iced coffee or iced tea for 99 cents. Note there is a limit of 2 per person and like most deals, this is only for a limited time. Also, in case you missed it a couple days ago, the AZFoodDude posted a story about the new Dunkin' Donuts Blueberry Waffle Breakfast Sandwich going for $2.99.
Update (5-18-2011): This deal will expire on Sunday, May 29th.