The Gong Project

I've been intrigued by the potential ESL applications of the voice bulletin board module from The Gong Project:

http://gong.ust.hk/

The program provides a simple method of posting threaded discussions containing both text and voice recordings, but the feature that fascinates me the most is the capability for the instructor to add a voice transcript with synchronized (and student/reader controllable) text highlighting:

http://gong.ust.hk/features_selectplay.html
http://gong.ust.hk/features_speed.html

Best of all, it's free! I've used Gong successfully both in my adult literacy/ESL tutoring and high school ESL practicum classes.

One caveat: Gong does have a moderately complex installation procedure on the server end, but the resulting system is very easy/intuitive for both students and teachers.