Yoga and general relaxation
One of the symptoms, and indeed often argued on a self-perpetuating basis as one of causes of stuttering, is general anxiety or stress. This is normally attributable to a specific speaking situation where the stutterer feels they will be disfluent. It seems reasonable to posit that reduction in general stress levels will be positive for fluency. One method for relieving stress is the practice of specific types of yoga
There are many types of yoga, and each has their own place and purpose. It is not intended to even attempt to describe the area or introduce the topic; rather certain types of yoga have be selected as possibly pertinent to the development of fluency. These selected areas are certainly not exhaustive, and there may be other relevant yogic practices which have been overlooked in my ignorance.
Pranayama
Many of the programmes developed to alleviate stuttering involve at least an element that relates to breathing, whether it be deep breathing, or a specific way that the postulant must learn to breathe. Pranayama, the control of lifeforce (prana), involves the regularisation of breathing through a specific nostril. The three stages are inhalation, holding, and exhalation. As the practice develops, the duration of these stages increases and the ratios between them are also altered. Adherents generally use the index finger to close the air passage to the other nostril. There have been claims made that it does in fact reduce stress related conditions, and some even claim that regular practice increases lifespan. Pranayama is considered one of the more obscure legs of Raja Yoga and is generally not recommended for beginners. Personal instruction is recommended. I have experimented with it and found that it does seem to work (in some circumstances), and it does increase general relaxation. It is likely to be most useful on those days when you feel that an oppressive cloud of stress/disfluency is hanging over you to help to reduce the general level of stress experienced. It could also be useful before specific feared situations such as a presentation or interview, where the practice of it beforehand may decrease overall stress levels. Apart from its effect on level of fluency, it is likely, if properly practiced, to decrease overall stress levels and have a postive effect on the practictioner's overall health.
Asana
Again, this practice is related to some of the more general methods for alleviating stuttering. Asana relates to posture, and it is recommended that it be practised in tandem with pranayama for a best results. There are many different asanas (positions) and again it is recommended that instruction should be interpersonal. Its practice should increase tendon and muscle strength, and on a more esoteric level increase the flow of prana.
Dharana
Dharana is a branch of Raja yoga which relates to concentration. This is something which has been advocated in the past as a methodology for dealing with stuttering, specifically in the context of phone conversations where the person you are talking to are not in front of you (and thus you can't retain eye contact). The stuttering methodology involves choosing an object (say from the wall in front of you) and then concentrating on this object for the duration of the call. Dharana takes a more mystical approach but arguably may end up with the same result. Rather than concentrate on a banal object, practictioners may choose to concentrate on a specific tattva
Mantrayoga
Mantrayoga is associated with pranayama. As its name suggests, it involves the repetition of a mantra which should eventually lead to a state of dharana. Its practice may have an additional benefit for the stutterer as they are exercising their vocal equipment as well as sliding (see voluntary stuttering) the words that make up the mantra being used. It would also be interesting to experiment with using a mantra of a feared word (say perhaps your name) to see whether any positive effects, whether desensitisational or enunciational were produced.