There are on average about ten volcanoes erupting on earth on any given day. Most of these events are small eruptions that may be precursors to larger eruptions. There have been many cataclysmic eruptions in historic times. Since 1800, there have been 19 eruptions on earth in which a thousand or more people have died (see historical eruptions map).
For global data on current eruptions see: Update on Current Activity (Volcano World) or Global Volcanism Program: Worldwide Activity.