Harold D. Underdown
The Purple Crayon: Writing Dazzling Dialogue
This site takes you through the process of writing dialogue in fiction, demonstrating when to omit, replace, or modify your original writing. Includes several examples and gives excellent advice for young writers. W.9-10.3b Narrative...
Caro Clarke
Caroclarke: Dialogue: The Best Action
This is the fourteenth article in a series published with the goal of helping the new novel author. This article focuses on using dialogue to advance the action of the story. Links on the left offer other information about story writing.
Other
Writing world.com: Writing Dialogue for Children
A good site for teachers and writers looking to write for children, or teach children how to write dialogue. Includes tips and guidelines.