It has been seen that if you can change your stammer a little bit- just a wee bit, you can eventually change it a LOT. You can almost modify it to appear normal! So, can you modify the way you talk? Just for fun? Just for few minutes? If you talk in a fixed, frozen way and believe that this is the only way you can talk- if you believe that you can stammer just one way, your way- then, path ahead is difficult. But in our experience, every PWS is capable of making small changes at a time- and a lot of changes over a period of time.
You must have tried your hand at mimicry or taken off the boss in office just for fun- or may be you like to deliver the famous dialogue from Deewar, in Amitabh Bachhan's style and his baritone. May be you think that you are not good at these things- but if you have tried a little bit, you can try a little more, especially if you know, that this is the key to your problems. Yes, it is.
A) Vocalization exercises:
It will be good if you begin with some relaxation exercise- Inhale deeply and tense all muscles, beginning from feet, hold the tension for 2-3 minutes and then gently relax whole body in the reverse order- as you breathe out slowly. Next, you sing out consonants in all combinations of vowels (Ka, ki, ke, ku, ko, mi, me, ma, mo, mu etc.) in a relaxed and stretched way: kaaaaa... Kiiiiiii...... etc. (Look at this video for better understanding: http://www.ehow.com/video_2385250_the-mi-ma-mo-mu.html)
After one full cycle of all consonants, start a new cycle, wherein you add variations in volume (low, almost whispering and then raising it to a loud shout and then again back to a whisper). Next, add variations in pitch- put a hand on your throat to get the feel, as you manipulate your vocal cords to get a high note (kiiii...), followed by a very base note.
Most attempts at personal change fail to sustain, because they are often devoid of FUN. A fun way of beginning this journey would be SINGING. First, sing alone, record it and review it. Begin with simple popular songs. Try to pay attention to notes, melody and rhythm. After a few recordings, you will feel good about your singing abilities. Next, sing for a friend, who stands a little away. You may also try reciting shloka, chants, poetry, shayari etc. Consider learning classical vocal music.