Sitka was the Russian capitol of North America, back in the days before the U.S. purchased Alaska. If you have a good long day in Sitka and aren't mobility-impaired, the advice about walking around town is good. We did a combination of a tour to the Raptor Rehab Center (for injured eagles/owls/hawks etc.) and a walk on the National Park trail - nice walk in the forest, with totem poles placed along it. On the way back, we opted to walk into town, as it was only 1/2 mile or so. We walked by another National Park site, the Russian Bishop's House, and went in. For $5 each (I think), we got a great personal tour - the lower floor has artifacts and various displays that gave a lot of insight into the Russian settlement and culture there. The upstairs is restored to the condition it was in when the Russian bishop lived there, complete with large parlor and personal chapel. Well worth the stop. This last part was done completely on our own.
I believe Hubbard Glacier is not a port call, rather a day spent onboard, cruising slowly by and stopping at the glacier for a great view. There may be a naturalist onboard (if you're on Holland America, it's likely) to offer more information on what you are seeing, and answer questions.