Pinyin Pronunciation Guide- Learn Chinese ABC

Check out this website by Learn Chinese ABC.  It provides a brief introduction to the history of pinyin development and also provides in-depth and accurate information about how to pronounce these sounds.  The description of each sound is complimented with an animated video of the articulators (teeth, lips, palates, and tongue).  This allows you to see exactly how to position your tongue for each sound.  In addition, there is also written step-by-step instructions to follow and video of a native-speaker as they say the individual sounds.

To access the free site, click on the link above and then use the topics along the left-hand side.  This site is a little visually overwhelming, but if you take the time to accustom yourself to it you will find it is a wealth of information.