I was in Alaska last September. It depends on what kind of cruise you're looking for.
I got a cruise in Seward with Kenai Fjords Tour (http://www.kenaifjords.com/). It's a one-day cruise; the fjords are really amazing! and if the conditions are good, you can see eagles, sea lions and maybe whales. about 5 years ago
I am a travel consultant. There are several large cruise lines. Princess, Celebrity, Holland America, Norwegian Cruise Line. They depart from Vancouver, BC or Seattle. You can do 7 days round trip, 7 days in one direction and get twice as far up the coast in Alaska and then do a land tour or fly back. You can do southbound or northbound on these one ways. I recommend Holland America, Princess or Celebrity. about 5 years ago