http://www.walgreens.com/topic/promotion/seniorday.jsp
The first Tuesday of every month you can save 20% at the Walgreen store on Sheldon in the Depot Shopping Center next to Albertson's.
You must be 55 or older and have a Walgreen's Balance Reward card which is free or be a member of AARP.
The above link says just one day, but the store says it's every month.