Help your volunteers remember all the kids in the classroom by presenting them with personalized class photos. Blow up an image of the students, and have the kids sign their names around the photo. Make copies of the picture and frame them in inexpensive frames from a dollar store or budget home goods shop. Give the gift with a nice note that the students can all sign as well, making for a meaningful gift.
Get the kids involved in making baked good presents that parent volunteers will enjoy. Pick a no-bake recipe like cereal crisp treats or candied apples, and make a project of letting students put together the treats. Package the items in decorative baskets or boxes that the kids can decorate during art period, and add each parent volunteer's name to one of the baskets.
Make unique parent volunteer gifts using fabric items such as plain aprons or baseball caps. Have kids use fabric paints to decorate a canvas apron with handprints. Or have students sign their names to a plain baseball cap with a felt marker or fabric paint pen, with the words "Thank You" written above. This is especially nice if the students are learning and practicing their writing.
If you have a parent who goes out of his way to help with school field trips, either organizing permission slips or acting as a chaperone, give the parent a souvenir from the trip that will show your gratitude and act as a reminder of the day. If the class visits a museum exhibit on mummies, give the parent a small mummy figurine from the museum gift shop. If the class visits an orchard in the fall, give the parent a basket of apples the class helped pick.