The ferries are another 3 miles north. There are some good trails in the area, as well as fishing. The buses also run around Back Loop Road, which gets you within a couple miles of the camping and hiking areas on the east and west sides of the Mendenhall Glacier. The bus turns off about 2 miles from the visitor's center, it doesn't go all the way to the glacier. There are cabs and shuttles, and prices vary.
Bikes are a great option, and rentals are available.
There are a number of places that rent kayaks and gear, as well as guided trips. Virtually all offer camping possibilities. There are also excellent guides to plants, birds, marine mammals and wildlife, written and illustrated by local experts. There are three branches to the public library, in Mendenhall Mall in the valley, in downtown Douglas, and on the waterfront in downtown Juneau. It's a good rainy day respite.