The Franklin Institute
The Franklin Institute Online: Earthforce in the Core
This site from The Franklin Institute Online takes you to the core of the earth and discusses how volcanoes are formed. Provides links to general volcano information as well as volcano science and teacher resources.
University of Hawai'i
Ask an Earth Expert: What Are the Different Types of Volcanoes?
A concise explanation of the three types of volcanoes recognized by geologists.