Inhabited Madeline Island makes a fine day trip and is reached by a 25-minute ferry from Bayfield. The isle's walkable village of La Pointe has a couple of mid-priced places to stay, a smattering of eateries and a groovy 'burned down' bar (made from junk and tarps). Bike and moped rentals are available – everything is near the ferry dock.
And FYI: while Madeline is an Apostle Island, it's not part of the national park group, hence its development.
