Portage Glacier is a road-accessible glacier located about 50 miles south of Anchorage, about 5 miles off the scenic Seward Highway.
It makes an excellent stop for travelers heading for cruise ships at Seward or Whittier, particularly if you take the short cruise available on the MV Ptarmigan.
In any case, a visit to the Begich, Boggs Visitor Center is highly recommended.
A hike to the Byron Glacier, between the visitor center and the boat dock, allows you to walk on a glacier.