The Complete Idiot's Guide to the American Accent
OK, I'm a bit offended by any book with "idiot" in the title, but I'll nevertheless let you know that the Penguin Group has published an "idiot's guide" to how one can refine his or her pronunciation of English.
The Complete Idiot's Guide to the American Accent contends that "when a person speaks with an accent that is not customary, listeners pay less attention to what is being said." At the same time it advises, "Don't set the bar too high. Work on improving your intelligibility, not eliminating your accent. As long as you can be clearly understood, an accent can make you more interesting, and even intriguing, to the average American."
I have interviewed English-language learners who are sensitive about their accent in English. Sadly, sometimes they get teased by other students for it. And I remember interviewing one ELL who was fluent in English but was very difficult to understand, as she'd learned English from teachers in her home country who had non-standard pronunciation. I needed to ask her to write some words down for me during our interview and she patiently did so.
I bring to your attention this guide to developing an American accent because it does contain pronunciation exercises and a CD that might be useful for some ELLs who struggle to speak clearly enough to be understood. It has exercises, for example, to tackle "consonant troublemakers," such as the voiced "th" sound and the unvoiced "th" sound.