Following is a really good website for better Mandarin pronunciation:

www.speakchineseonline.com

I've been looking for a site like this for a while.  What's so great about it is that it describes each pinyin initial and final, using animation with sound, step-by-step description (with visual of what the lips, mouth, tongue, etc. do), and video/audio of an actual native speaker.

It's similar to CPod's Pinyin Chart, but with video and better description of what the mouth does.  There's other good info. on this site as well.