Here is a website that has lots of info on the AK portsAs an FYI, Carnival also offers Glacier Bay cruises at the start and end of their season. We also live in Seattle and have done this in the past. It's shoulder season so the rates are generally pretty good (and if you're from the NW a little rain won't get you down
I agree that Glacier Bay is a must see - the cruise lines that vist there are limited to Princess, HAL, and NCL.
For those mentioning Amtrak it's a pleasant trip on the coast and I'd also recommend it. The light rail station is right near Amtrak in Vancouver and has a stop near the port so it is pretty easy to get to the port on the cheap.