USA: The First Online Conference on Cluttering (2010, April 14- May 5): http://www.mnsu.edu/comdis/ica1/icacon1.html
USA: The Stuttering Homepage (contains multiple pages of interest with regard to cluttering); particularly of interest is: http://www.mnsu.edu/comdis/kuster/cluttering.html
USA: The Stuttering Foundation of America also has several resources with regard to cluttering
The brochure "CLUTTERING some guidelines" (by Kenneth StLouis)
The brochure "Stuttering versus Cluttering" (Kathleen Scaler Scott) available from the National Stuttering Association
The DVD "CLUTTERING" by Kenneth StLouis, and Florence Myers.
UK: speech samples (*.wav files) made available by Peter Kissagizlis:
Cluttered Speech when speech is slowed down: Link currently not available
See also a video recorded speech sample containing cluttering (available on Stuttering Homepage (www.stutteringhomepage.com) :