Hi, Cat. I put a list of some resources here (check the next page of that thread for one more, with the Colosseum on the front, no less!):
http://giftedissues.davidsongifted.org/BB/ubbthreads.php/topics/89030/1.html

I can't vouch for most of them based on first-hand knowledge, since money is tight. That Greek and Latin Roots series seems like it might be right up your son's alley. Maybe you could bring those up on bn.com or amazon.com and browse around the "other suggestions" links at the bottom to find more in a similar vein.

Striving to increase my rate of flow, and fight forum gloopiness. sick