http://www.wordcentral.com/home.html
Merriam-Webster’s Word Central is an online dictionary resource for kids. It offers a thesaurus and rhyming dictionary, as well as daily word challenges. I know that we had some issues finding a dictionary that would serve the purposes of our grammar studies, but had no luck finding a good combination. This online resource may not get your children learning alphabetical order, but it may make looking up and learning new vocabulary more fun!