What are some ways that plate movements create volcanoes?

Note,
the explanation below is a vastly simplified version of reality. If you wish more accurate / detailed explanations i suggest you take a course or two in geology 101.

plate movements can be simplified into 3 main types - 2 of these are likely to result in volcano creation, the other isn't.

1 - when plates move in towards each other 1 plate moves over the top of the other. This is called a destructive plate boundary or a convergent plate boundary. The plate that is pushed downwards gets heated up and some of the rocks melt, forming magma, which then rise back up and form volcanoes.
Mt Fuji (Japan) is an example of this, as is Mt St Helen's (USA)
simple explanation with nice images

2- Constructive (or Divergent) plate boundaries occur when plates move apart from each other. As both plates are moving away from each other the Earth's mantle (liquid) fills the gap. This mainly happens under the sea, so causes underwater volcanoes and also occurs on the Island of Island (as part of the mid-Atlantic ridge).
again, same site, nice images

3- the third type of plate boundary neither creates nor destroys the plates. This occurs when plates move at #180^@# to each other. Commonly called conservative plate boundary or transform boundaries. These types of movements rarely cause volcanoes, but are associated with earthquakes (ALL types of plate movements are associated with earthquakes - if the Earth's crust is moving it should not a surprise that it quakes!)