Articulation is defined as the act or manner of producing a speech sound
The following articles are provided for your reference from Super Duper Publications and other resources.
Speech Sound Development Chart
Articulation Practice at Home
Placement Cues for Articulation
What is a Lisp?
Oral Motor Workout
Summer Activities
http://http://mommyspeechtherapy.com/?p=1502
Speech Helpers
10 Ways to Improve Communication