Clifford the Big Red Dog
Clifford's Word Book
Clifford the Small Red Puppy
Clifford and the Grouchy Neighbors
Clifford's Best Friend
Clifford's Class Trip
Clifford's Spring Clean-Up
Clifford and The Runaway Rabbit
Clifford's First Day of School
Clifford and the Big Parade
Clifford's Happy Mother's Day
Clifford's First Valentine's Day
Clifford's Pals
Clifford's Manners
Clifford Takes a Trip
Clifford Goes to Dog School
Clifford Gets a Job
Clifford and the Big Storm
Clifford's Sports Day
Clifford's Day With Dad
Clifford's Puppy Days : The Smallest Snowman
Clifford's Puppy Days: Puppy Love
Clifford and the Big Leaf Pile
Clifford's Puppy Days: Skating With Friends
Clifford and the Stormy Day Rescue
Clifford Grows Up
Clifford to the Rescue
Clifford Keeps Cool
Clifford We Love You
Clifford's Riddles
Clifford Visits the Hospital
Clifford's First Snow Day
Clifford's Good Deeds
Clifford and the Big Ice Cream Mess
Clifford at the Circus
Clifford's Happy Easter
Clifford's Tummy Trouble
Clifford's Loose Tooth
Clifford's Hiccups
Clifford's Tricks
Clifford the Dog Who Cried "Woof"
Clifford and the Show and Tell Surprise
Oops, Clifford
Clifford the Firehouse Dog
Clifford's Puppy Days
Clifford's Kitten
Clifford's Puppy Days: The Little Red Sled
Clifford's ABC
Clifford's Birthday Party
Clifford's Christmas
Count on Clifford
Clifford's Family
Clifford's First Christmas
Clifford Goes to Hollywood
Clifford's Halloween
Clifford's First Autumn
Clifford's Thanksgiving Visit
Clifford's First Halloween
Clifford's Puppy Days: The Little Blue Easter Egg
(These are just the Clifford books I own, I'm sure there are many more!)