Saying the Letter A (or any letter from the alphabet) over and over again. Use only one letter since on their own they are meaningless. Just keep repeating it. It seems after about 30 minutes of doing this the habit of subvocalisation can be broken.
Counting and reciting the alphabet is less effective. The one letter said over and over is a meaningless sound. Try combining it with nature soundtracks like ocean or waterfall. They also reduce subvocalisation.
In all if you do all the photoreading steps it doesn't really matter if you subvocalise. I find that my reading speed has rocketed. As for the subvocalisation it's actually a habit I am not in a hurry to get rid of myself. Hearing the words said in my mind keeps them alive in my spoken vocabulary. 
Alex
[This message has been edited by AlexK (edited December 02, 2002).]
