A department at University of Iowa has made available a very useful resource for English pronuciation leaner - The Phonetics Flash Animation Project (see project page).

Here is a short description to the site:

This site contains FLASH animated libraries of the phonetic sounds of Spanish and English. Available for each consonant and vowel is an animated articulatory diagram, a step-by-step description, and video-audio of the sound spoken in context. ...

The site feature Phonetics Flash Animation of three languages including "American English".  You can go directly to the American English flash animation using this URL http://www.uiowa.edu/~acadtech/phonetics/english/frameset.html.

The gem is hidden under the interface, however.   In order to get to the flash video clip demonstration of sound forming (as well as toung position) on must know where to click.  

To make it easy to reference, I have put reference to U of Iowa's flash animation project for each of the sound separately. (See Subpage Listing)