All the really cool excursions are pretty pricey.
For the 2011 cruise, we had ZERO money for excursions, so our son went gold panning ($20) in Skagway
my wife took a tour of the state capital (FREE) in Juneau
and I hit the Alaska Brewing Company ($15?) in Juneau
For the 2013 cruise, we took the White Pass Railroad in Skagway. It's fairly pricey and something I probably wouldn't do again. Beautiful scenery though.
In Juneau, we took the bus to the Mendenhall Glacier. We'll do that again. I don't think they gave us enough time there though. We also took the Mt. Roberts tram. That was just OK.
In Ketchikan, we took public transportation to Totem Bight State Park. I thought it was kinda cool, until I realized all of the totems were replicas. Ugh!
The best day by far is the Tracy Arm Fjord day. So beautiful and Disney does a great job of getting you VERY close.