Speech and Dialect Resources
GeneralAmericanAccent.com - Kate DeVore's speech training manual with downloadable audio.
AccentHelp.com - Downloadable accent and dialect training materials and training.
IDEA: The International Dialects of English Archive - Free audio clips of speakers with various accents and dialects.
Paulmeier.com - Dialect materials and training.
Voice Resources
Journey of the Voice - Anatomy, physiology, and care of the voice.
Voice & Speech for the Professional & Aspiring Actor - Warm-ups, voice exercises with downloadable audio, and blogs.