Right up my alley here, both as a teacher and a mommy to a three year old. Both of the above mentioned books are hits with my daughter. Some others are "Crysanthemum" and "Lily's Purple Plastic Purse." "The Little Engine that Could" is another we are reading ALL the time right now.
At this age, they also love any books with their favorite characters--we read Clifford and Dora books far more than I would like.
Curious George books are fun and so are the Dr. Seuss books, especially "Green Eggs and Ham" and "Fox in Socks"
Others I can think of sitting at the computer...
Any of the series of books by Laura Numeroff ("If You Give a Mouse a Cookie," etc.)
The "Froggy" series by Jonathan London,
"Five Little Monkeys" books by Eileen Christelow (titles like "5 Little Monkeys Jumping on the Bed," "Don't Wake Up Mama!," "5 Little Monkeys Wash the Car"...)
Jan Brett's books ("The Mitten," "The Hat," "The Umbrella")
Oooh, I could keep going...better stop
Enjoy an hour in the children's section of your favorite bookstore!