The Cat In The Hat - This classic Dr. Seuss book (about a tall mischievous cat who is famous for his white-striped hat and red bow tie) includes multiple words with short vowels. One extension for this book would be to have children create a hat that is made of rhyming words. Once the hat is complete a connection can be made between words that rhyme and their vowel sounds.
Life in First Grade: Classroom Decorating Day 7: See it Sort it Pocket Chart Center. I think this would be an awesome center for those who finish quickly. I would send them over there and tell them to make some words using this week's vowel sound.