On trip advisor, type in Ketchikan. Go to "things to do" - gives you a list and descriptions of what other people have enjoyed (or didn't enjoy) in town. Also, click on "tours" in the "things to do" section - gives you ideas on various tours and how people liked them.
I've been reading Frommer's and Fodor's - they give good walking tours, maps, and more ideas. Too much to see in one day, so see what appeals to you.
You can also do a search on cruise critic (Boards) for Ketchikan.
Duck tour, Creek St., ride up to Cape Fox Lodge, bus out to one of the totem parks, Lumberjack show, Wild Alaska Stunt Show, SE Alaska Discovery Center, flight to Misty Fjords,