Here are some reccomendations, I actually sail in one week for back to back Alaska cruises on the Statendam May 6-20. These will be my 5th and 6th trips to Alaska.
Ketichican
The totem parks are OK, nothing special for me. I tried a flight to Misty Fjords a couple of trips ago but didn't get there because of fog. If you fly here try
www.islandwings.com , they offer a cheaper, longer tour than the ships excursions.
Skagway
Everyone does the White Pass train ride, if you do sit on the left side going up. Personally I would do the 1/2 train,1/2 bus or even better the trip into the Yukon.
Also join up with one of the free Ranger led walks around town to learn about the colorful history.
Juneau
This is the place to get up into the air and do some flightseeing. Haven't done the helicopter trips yet but have done the glacier flight and the Taku Lodge trip. The best value for your $$ is the glacier flight which I plan to repeat on this trip. Also get out to the Mendenhall Glacier if possible, and the Mt Roberts tram is also very nice. Don't buy this through the ship in case of bad weather, price on the dock is exactly the same and you can decide them if visibilty warrants the trip.
Sita
Unless you plan on a wildlife cruise you are better off on your own here.(if you don't mind walking) The state park has a very nice nature trail with many totem poles along the walk. This is about 1 1/4 miles from the dock. Just up the road is the Raptor center, maybe only another 1/2 mile. Total walking tour of town would probably involve a 2-3/12 mile walk and only cost the price of admisson to the Raptor center. Instead of a $40+ ship tour pp it would probably cost you $10 plus some exercise.
Seward
If you have the time here the tour to Exiot Glacier is nice, along with teh Sealife Center. I plan on taking an all day cruise to Misty Fjords this trip.
You will love Alaska, scenery is fantastic, My overall glacier preference is College Fjord, Hubbard Glacier with Glacier Bay last but still spectacular.
Doug