Volcanoes by 
Volcanoes and Earthquakes by 
Earth's Fiery Fury by Web Resources:
Michigan Tech - A ton of Volcano links!
USGS Volcanoes Maps, Images and Publications
NASA What is a Volcano?
HowStuffWorks How a Volcano Works
PBS Savage Earth Volcanoes - Information, Animations and Video
NOAA Volcano Images, Data and Information
Ready.gov – Volcano Preparedness and Safety http://www.ready.gov/volcanoes
Red Cross Volcano Safety http://www.redcross.org/prepare/disaster/volcano
Volcanoes and Volcanic Hazards – A video of a slideshow. Very detailed and long, but a ton of information with diagrams!
Scholastic Lava-licious – Using chocolate and marshmallows to demonstrate the properties of lava!