Visiting Skaftafell in the south of Iceland provides a seemingly limitless amount of activities.
I went on a 4 hour glacier hike across Svínafellsjökull and it was worth every heavy, crampon-laiden step.
From the visitors center, there are a couple of main guide options available and they're both great, although I went with Icelandic Mountain Guides.
My primary tip, go early. Get yourself on one of the morning trips when the glacier is empty. As the day wears on, more groups can be seen across the glacier and it's just a little more fun when it seems like you're alone on this river of ice.