I've recently discovered ZapReader tracking through some links on LifeHacker. It's a speed reading assistant that flashes words of the text at you at a certain rate. Seeing one word at a time didn't seem like a good idea, since I had always tried to read in phrases in my previous speed reading attempts. Fortunately, ZapReader lets you configure the number of words it shows you at a time, so I set it to 4 words at 600wpm, and I've found I can just barely keep up. That actually doesn't feel too bad. I'd love to see the thing be able to break on phrases more intelligently than just word count.
My biggest problem has always been subvocalization -- I have so much trouble getting the little voice in my head to go away. This tool may help with that, and hopefully the habit will go away for printed text as well.
I've added the little ZapRead bookmarklet to my FireFox link bar, so I can select any text and have it "Zapped" at me.