Ohio.edu : Speaking : Pronunciation. A set of links to pronunciation directories, phonetics, American English vowels, sentence stress in English, course on phonology etc. For all levels.
Pronuncian.com: A series of nine short lessons with video segments
about sentence stress in American English. Topics covered are:
Introduction to Sentence Stress; The Rhythm Rule; Negatives and Not;
Neutral Sentence Stress Guidelines; Sentence Stress: Nouns and Main
Verbs; Unstressed Words; Sentence Stress: Descriptive Words; Open
Compound Nouns; and Phrasal Verb Stress.