In my book I discuss how non-native English speakers can find ways to improve their spoken English. Spoken English skills consists of two major areas: 1) vocabulary and usage, and 2) accent. English intonation, especially the American one spoken in the U.S., is quite difficult to adopt for most non-English speakers. The way words are pronounced individually as well as together carries a lot of subtlety that anyone who starts to learn the language after age 4 or 5 will find very difficult to master.
About ten years ago I found a CD set at my local Barnes & Noble which supposedly would help one speak American English better. It’s now available on Amazon for a little over $26:
I myself found the CD set marginally helpful (after having lived in the U.S. for ten years, having arrived here in my teens). If you find yourself speaking American English with a heavy foreign accent, this 5-CD course may prove one of the better investments you’ll make in improving your career prospects. (Another worthy investment for would-be quants is the nice book by yours truly, of course! )