The Stuttering Foundation is a non-profit organization whose aim is helping those who stutter.  It's website provides information, advice and resources for children and adults.  

The American Speech-Language Hearing Association (ASHA) is the national professional, scientific, and credentialing association for 186,000 members and affiliates who are audiologists; speech-language pathologists; speech, language, and hearing scientists; audiology and speech-language pathology support personnel; and students. Audiologists specialize in preventing and assessing hearing and balance disorders as well as providing audiologic treatment, including hearing aids. Speech-language pathologists identify, assess, and treat speech and language problems, including swallowing disorders

Super Duper Handy Handouts

Super Duper, the makers of many speech-language and learning materials, provide free, informative handouts on a variety of topics ranging from sentence structure to apraxia.  

https://www.superduperinc.com/Handouts/Handout.aspx