Poor pronunciation has held many of my professional students back in their careers; they either couldn't be understood as well as they needed to be, or they were too self-conscious to speak up because they were afraid they wouldn't be understood. The classroom could never give them all the individual coaching they needed.
I have recently found a remarkably useful and well-designed tool, Pronunciation in American English. This CD-ROM is successful because it is interactive; it has a record and playback function as well as video and audio examples. Students can instantly hear the difference between American pronunciation and their own. It also focuses on what will make a real difference in their being understood: stress, intonation and rhythm.
My students have found Pronunciation in American English both user-friendly and interesting. It is self-paced and takes about 30 hours to complete. Because it focuses on the language they need, it has kept students engaged and learning to the point where I could hear real improvement in their speech. Previously, I had often seen my students reach a plateau in pronunciation improvement. Pronunciation in American English has pushed them past that plateau to a new level where fossilized problems have been corrected.
I don't always agree that a high tech solution is better than what I could have provided with cassettes or classroom instruction, but Pronunciation in American English gives my students what I could not; a skilled, private tutor who will be there at any hour of the day or night to give them exactly what they need. I wish I had such a CD for each of my college classes.