Skagway: I suggest the White Pass rail trip. Especially good if you like history...and trains.
Juneau: Take the bus from the dock at $10 round trip per person to the Mendenhall glacier. I think the visitor center's an extra $3.
There is a small viewing platform at the far end of the parking lot. I believe it's actually for bear viewing. Even if no bears you will see salmon spawning.
Mt Roberts tram is also right at the dock. A beautiful view from the top. Don't need to pre-book either. If it's cloudy or rainy you won't want to go up. Not for you if you're afraid of heights.
Whale watching with Orca enterprises (Capt. Larry) is terrific. You will see humpback whales upclose and personal. Possibly Orca as well.
Ketchikan: Duck tour is silly but fun. Just walking up to Creek street is really nice. Take the funicular up and walk down the married man's trail. There are totems up top by the hotel there. The salmon ladder is next to Creek street as well.
We went on the Diamond last July and I agree with halfdome on the excursions in Skagway & Juneau they are the best. If your interested in go-karting in the wilderness in Skagway it is a blast, hubby and I did it and really enjoyed it, booked it through Princess.
I agree with the recommendation for the White Pass and Yukon Rail trip. We initally though that $99 was a little steep for a 23 mile train ride, but it was breathtaking. The train itself was really nice and well restored and the narrator through the entire trip was informative and light. You'll have a great time. Bring lots of film, disks and memory cards!
In Juneau, you have to make time to go to the Red Dog Saloon. The singer/entertainer was a hoot! The place is a lot of fun and the food there, was very good too. The city itself was mystical.
The Mendenhall Glacier was very nice also. We couldn't believe the amount of people that were swimming in water a half a mile from the glacier with huge chunks of break ice floating among them. Go for the taxi, although the tour driver was very informative also.
Ketchekan was just beautiful. Foggy, misty and all. The Lumberjack show was well worth the moey and very entertaining. The bar across the street gives you a free glass when you buy a beer with the coupon from the show. The salmon were jumping out of the water right along the roadway behind the show area.
We wouldn't hesitate to go back in a hearbeat! We sailed the Celebrity Mercury on June 24, 05.
Just returned from a fantastic Alaska cruise on the Coral Princess.
In Skagway we rented a van (with another couple) and drove into the Yukon, as far as Emerald Lake. We rented our van from PB Cruisers, which I would not recommend -- go with Avis instead if you can still get a reservation. You will drive through much of the same area as the train, but will have the advantage of stopping when you want, etc. Easy drive -- can't get lost.
In Juneau we opted for a tour with Orca Enterprises, Capt. Larry. Excellent. We had pre-arranged for the van driver to take us over to Mendenhall Glacier and she wait while we walked around. We didn't have a lot of time in Juneau, so we weren't able to stay very long at Mendenhall.
In Ketchikan, we booked Island Air Wings for a seaplane trip into Misty Fjords. Gorgeous. Afterwards we lunched on Burger Queen (best fish & chips I've ever eaten) food while having a beer on the back deck at Artic Bar (across the street). Afterwards, we had a Highlights of Ketchikan Tour from Sourdough Tours. We went to Totem Bight AND Saxman Village, as well as a drive through the town.