My personal favorite is the White Pass Yukon route train journey in Skagway. Lots of history and an amazing scenic journey. Anne has a good article on shore excursions in our Alaska Plaaning Guide with lots of info and ideas you might want to check out.
Get a hold of a shore excursion list and narrow down your choices. Then repost, you will then get a lot of helpful information- but the best of the best excursions??? A glacier helicopter landing out of Juneau via Coastal!!!!