The following sites are official organizations.
The Stuttering Homepage : Very extensive links and information about stuttering.
The Stuttering Foundation : Free materials, eBooks, and online streaming videos for consumers as well as workshops and ASHA-approved CEU opportunities for SLPs. Newsletters and information on research are also available online.
National Stuttering Association : The American Organization for education and advocacy for people who stutter.
The American Institute for Stuttering : A new blog.
British Stammering Association: The official help guide for people who stammer in the U.K.