Gary H says:

Mt Saint Helens was a big one recently. Krakatoa and Vesuvius were big eruptions that occured within our recorded history. There were big eruptions that we know about only through geologic evidence. Craters of the Moon National Monument in Idaho is evidence of a very big eruption. The caldera that forms much of the geology of Yellowstone National Park is evidence of another. THe volcanic activity that has build the Hawaian Islands and Iceland qualify as big ones. If you do some research, I think you can find plenty more examples. Good luck