Over the last several summers, I helped run a theater workshop for teens. I noticed that one of the warm ups we use with young actors would transfer well to practicing fluent, accurate reading in the classroom.
One of the leaders would call out a tongue twister and the group would respond in unison. The focus was on enunciating and projecting, not speed. This practice works well in the elementary classroom.
I created a free eBook of original tongue twisters which can also be used to teach alliteration. Stop by this post on Artistry of Education to download Tongue Twisters.