
Here is a great website...1st International Collection of Tongue Twisters, you have to choose what language, and there are over 400 in English!
I did this with my children, some had lazy speech patterns. This helped immensely. I also have a daughter who performs, and has aced auditions because she does not trip over her words when she speaks. She is a nearly flawless tongue twister, reigning champion in our home...she unseated me in that title!