PBS
Nova: Build a Bridge
This exciting and interactive site illustrates the four main types of bridge building styles. Also contains games and hands-on descriptions. Appropriate for upper elementary and middle school students.
Tech4Learning
Pics4 Learning: Images for Education: Bridges
A large collection of beautiful photos of various bridges from around the world! A visual reference for teachers and students. Browse through the examples, then click to enlarge.
Merriam-Webster
Merriam Webster: Dictionary Illustration: Types of Bridges
Labeled illustration of five types of bridges: beam bridge, truss bridge, arch bridge, suspension bridge, and cable-stayed bridge.