These aren't the first greener crayons we've posted about, but we like Crayon Rocks both for their environmentally friendly factor and their unique shape.
Favored by occupational therapists especially for use with kids developing fine motor skills, these are a hit with lots of teachers, parents and kids. Made in the U.S. of soy wax (a renewable resource unlike standard petroleum-based crayons), they transfer to paper in a smoother way, slightly more like painting.
A student box of 16 colors costs $5 or splurge on a box of 64 (4 each of 16 colors) for $18. Find them at Crayon Rocks.