Though some people consider it an impersonal gift, many teachers prefer a gift card because it allows them to purchase things that they want or need. If you know a teacher's favorite store or restaurant, you can purchase a card specifically for that business; or, you can purchase the type of gift card that he can use at any store.
Some teachers will appreciate gifts that they can eat--because it's consumable, it doesn't take up permanent space. Consider putting a twist on the traditional apple or something that you make yourself. Be sure that you are aware of any dietary restrictions she may have before you give an edible gift.
A charitable donation can make a great gift for a teacher--if you choose a charity that is meaningful to him. Don't assume that the teacher supports the same causes that you do. Ask if you are not sure.
Teachers routinely spend their own money purchasing the things that they need for the classroom. While this may not seem like a personal gift, you are actually saving the teacher money. Ask her what items she needs the most and purchase those. You can also purchase a gift card for the local craft supply store.
A meaningful letter showing your appreciation may be better than something you can buy. Be sure to be as specific as possible and mention how the teacher has helped your child. Better yet, send a copy of the letter to the school's administration so they know what a good teacher they have.
One way to get a really good gift for your child's teacher is to talk to the other parents in the class and pool your money. Even if each parent can only afford a few dollars, you'll see that the money quickly ads up. You can use this money to purchase event tickets or something else that she wants.