There are many wonderful show and tell ideas that allow a child to share what is most important to him with his entire class. For example, many student enjoy sharing vacation memories. On returning from a vacation, a child may return to school with a photo album filled with pictures of places he visited. He may also want to share things like souvenirs and guidebooks for the vacation destination. These kinds of ideas are good for educating the whole class about places far away, without actually traveling there.
Another popular idea for show and tell is taking souvenirs and literature to class from a museum that a child recently visited. This allows the child to fill his classmates in on interesting things he saw and learned on an educational trip, while also more firmly committing the details to memory. When a child spends time relaying experiences to her friends and classmates, he is much less likely to forget the experience.
If a child's mother is expecting a new baby, that presents a wealth of possibilities. For example, while a little boy's mother is pregnant, he could take ultrasound photos to class and explain all about his new brother or sister to be. When the baby is born, he could take photos of the newborn to school or even photos of him holding his new brother or sister. If his mom has a special stethoscope that allows her to listen to the baby's heartbeat at home, he might even take that for show and tell, demonstrating it for the class.
Pets and animals can also be good subjects for show and tell. If a child learns about certain animals at the zoo, he may take pictures to show his class. If he's just gotten a new pet, he may take in a leash, pet toy, or even a food dish to show to his classmates. If a pet is a small enough, the teacher may even allow it to come to school for a day. For example, if a child has a hamster, he may be able to bring it in its cage for a close-up show and tell presentation.
Show and tell ideas don't have to be complicated. Even something as simple as a favorite book can make a good subject. Likewise, a collection of rocks or newly fallen leaves can provide plenty to present to the class. The idea is simply to choose something that interests the child and allows him to tell his classmates about it.