I've been 3 times.
Helicopter tour in Juneau was amazing. On a second trip, my sister and I went whale watching, which was also worth it. We saw tons of humpbacks as well as some silly sea lions and bald eagles. It is a fun town to walk around too. Very good crab legs in a restaurant near where the ships dock. Can't remember the name. It is just south of the tram station.
Do the White Pass rail tour in Skagway.
Everyone should. There is a fossil ivory shop on a corner with gorgeous carved items and friendly, informative sellers. They buy the ivory from an island and it supports the Inuit population of the island. A nice souvenir.
Ketchikan I just enjoy wandering around. It is a quaint little town. Shop owners are friendly. Lots of little places to grab a snack. If you like coffee, pick up some Raven's Brew. It is roasted there.
Don't get sucked in by all the diamond and tanzanite pushing in the ports. Another nice souvenir is a small piece of gold quartz jewelry...mined in the area.
Have a great time.