This website was shared with our family by my younger son's speech therapist. He underwent speech therapy for L and R sounds for about six months while nine years old.
This site shows what the mouth parts do while making each letter sound. This can help people realize when they are doing incorrection actions with their tongue and lips to try to teach them the proper way.
Phonetics: The sounds of American English at University of Iowa website
If the link doesn't work go here http://www.uiowa.edu/~acadtech/phonetics/english/index.html then click on Library of English Sounds.