6 links
Atom Builder
pbs.org
A shockwave application that allows the user to add up and down quarks to a hydrogen nucleus to create a carbon nucleus.
Atomic Structure and Subatomic Particles
nyu.edu
Basics about atoms, including structure and behavior.
Elementymology and Elements Multidictionary
vanderkrogt.net
Explains the origins of the names of the chemical elements and lists element names in many languages.
Free Online Chemistry Games
sheppardsoftware.com
Several online games to learn about chemical elements and the periodic table.
How Atoms Work
science.howstuffworks.com
From How Stuff Works. A complete tutorial on atoms, including what they are, current issues, and activities.
The Bohr Model
csep10.phys.utk.edu
Includes a description of atomic theory, shockwave animations, and diagrams.