The IPA Chart
This website, built to accompany the book "A Course in Phonetics", opens with the International Phonetic Alphabet.
Click anywhere on the chart to hear examples of the sounds and to see spectrograms of them.
Materials that accompany the book are linked by chapter number.
The Extras section has more info on how to use this site, and links to examples from dozens of languages, some bonus audio for English phonetic transcription, and some cool xray and MRI movies of people talking.