Pronunciation is important!
Here are some links to useful and interesting sites and documents that can help you help others with their English pronunciation:
http://international.ouc.bc.ca/pronunciation/ (Includes complete Workbook and mp3 files for each unit to download.)
Don’t miss this one…with x-ray video of the mouth:
http://hctv.humnet.ucla.edu/departments/linguistics/VowelsandConsonants/index.html
http://hctv.humnet.ucla.edu/departments/linguistics/VowelsandConsonants/course/contents.html
http://hctv.humnet.ucla.edu/departments/linguistics/VowelsandConsonants/vowels/contents.html
http://www.uiowa.edu/~acadtech/phonetics/
http://pauillac.inria.fr/~xleroy/stuff/english-pronunciation.html