Create flash cards of three-letter words that use short vowel sounds. Pull them out when you have a few minutes between activities. Hold each card up so everyone can see it and have the class read the word in unison. After the class has read the word, say the vowel sound by itself. You can also give the flash cards to students for independent work.
Take a song like "Bingo" or "Old McDonald" and replace the "b-i-n-g-o" or the "e-i-e-i-o" with the sounds of the short vowels. Make sure you are using the short sound and not the long sound. Change the remaining lyrics to include the name of your school or members of your class. For example, if your name is Mr. Benson, you could sing, "Mr. Benson had a class, ah-eh-ih-aw-uh. And in this class were 12 great kids, ah-eh-ih-aw-uh." Make the lyrics silly or funny so your students will want to sing the songs often and reinforce the short vowel sounds.
Prepare a series of sentences that contain words with short vowel sounds, or choose a picture book like Dr. Seuss' "Hop on Pop" that you can read aloud. Assign each student a short vowel. Tell the students to stand up and wave their arms in the air when they hear their assigned sound as you read. Instruct them to do it silently and sit down again before you read the next word. Read slowly and give your students the opportunity to have fun with the assignment.
Create a poster for each of the short vowel sounds. Start the day by telling your students that today's class is brought to them by the short vowel sound you've chosen. Ask students to tell you words that use that short vowel sound. Write the words on the chalkboard as they say them. Throughout the day, return to the vowel with short activities such as picking a student or two to come up and write a word on the board that uses the short vowel sound of the day.
Divide students into five teams. Assign each team a different short vowel sound. Tell them they have five minutes to search the room and find objects that incorporate the short vowel sound. Have them make a list of each object that they find. At the end of the five minutes, have each group share its list and point to the object they found. As a variation on this activity, you can also have students search for words with short vowel sounds in books or on signs in the classroom.