Last year when I first started my blog I did a post about back to school and getting the correct dictionary for your child. Here is the link to my original post. In this post I describe how most dictionaries are pretty much the same but it is important how comfortable the child is using it. This of course holds true for a thesaurus and other books of reference. When I wrote last years blog I hadn't gotten the knack of linking to books and photos. Here is a list of Dictionaries that might appeal to children. Remember if a child doesn't feel at ease using a reference book it will never get opened.
Scholastic Children's Dictionary (2010 Edition) This is new and updated for 2010.
Merriam-Webster Children's Dictionary from Dk Publishing. This was last updated in 2008 but it is still quite viable.
Merriam-Webster's Elementary Dictionary which was last updated in 2009....this is for older kids. I like the graphics in this one.
The American Heritage Children's Dictionary from Houghton Mifflin also from 2009. This was my favorite when I was young...well of course not this edition but you get what I mean. I liked how it was presented and at that time they were one of the first to use photographs as part of their descriptions.