Be sure to check out http://www.toursaver.com/
if you want to save a fortune on excursions to Alaska.
I travelled on Spirt two years ago (ready to go back) and without this book, couldn't have done half of what I did.
Most of the companies the cruise line books are also in the discount book, so don't be surprised if you find your cruisemates on your discounted tour.
Also, if you book morning excursions, you never have to worry about missing the ship -- and all the companies I worked with were so focused on ensuring you made your ship it wouldn't be an issue. In fact, one excursion I booked (not with the ship) had a late start due to problems offloading the ship. Since we lost time on the excursion, they made arrangements for the cruise to issue a partial credit to the guests (even those that didn't book it through the ship).
BTW, I may be interested in joining on a AK cruise... let me know if you're still looking for anyone.