I just returned from there and the Mendenhall Glacier was one of my two excursions. We did the "off track" hike over to the waterfall and it was well worth it. It's a bit of rock scaling and stepping through low streams but it was also a blast. It gave us a better view of the huge chunks of glacier that were floating out and lots of up close photos of the waterfall and glacier itself.
The bus tour stopped at a salmon hatchery on the way - which was unexpectd. And our guide Ken Jennings (not of jeopardy fame he reminded us) was fantastic. He pointed out a bunch of bald eagles and gave us a really good guided tour up to the glacier and back. He also stopped at a great viewpoint and let us all get out and take extra post-card-esque photos.
This was a Holland America excursion btw. I think it was around thirty-five dollars?? It was a gift to me so I'm not really sure. It was well worth every cent, I think.
My roomate did the helicopter tour to a glacier and said it was the best excursion that she went on the whole trip.