Both Franz Josef and Fox have organised hiking trips on to the glacier. The half day one i did on Franz Josef only goes a few hundred metres up the ice, but you can also do a full day, or heli-hike which means flying higher up and then walking.
You approach the glacier by walking up the boulder strewn valley where the ice had been previously. Its roped off about a half kilometre from the face and only organised trips are supposed to go further. Lots of people ignore that, but the day after i was at Franz Josef, 2 brothers at Fox ignored the ropes and went up to the face and were killed when tons of ice fell off the face and crushed them. So you gotta be careful, accidents happen even on the organised trips. the group in front of us had someone break a leg and have to be airlifted off the face!. With crampons on its quite easy walking up the ice, but there are steep parts. The organisers of the trips have built walkways and staircases on lots of it, but becasue its constantly melting, they take a pick on each trip and make modifications as they go along. The bottom part of the glacier is pretty grubby, because of all the rock brought down the valley by the ice. Apparently it takes on average about 65 years for something at the top to travel the 12 km or so down the glacier. As you get higher, you get past the dirty parts, and the blue ice is pretty spectacular.