Lucid dreams can be a great place to practice things for waking life. I use LDs for things like this often.

I would suggest, just because you can't take a "magical potion" in waking life, that you use LDs to practice speaking. Also try to discover why you stutter, then to deal with the reasons.

Using LDs to talk directly to your subconscous mind (which I bet is responsible for the sutter) is a great way to deal with psychological issues. Try to make friends with your subconsous. See what it has to say directly, and in the symbols and events of your dream.

I have a cousin who used to stutter. He said that when he slows down, takes a deep breath, it can help.

Good luck! You can do it!