I have one of those spelling-minded kids, too. He LOVES to spell. In fact DS won the 2nd grade spelling bee today.
DS and I have both been frustrated with his 2nd grade spelling words. Frankly, they're easier than the 1st grade words: more, store, pour? Seriously, in 2nd grade?
Merriam Webster partners with the Scripps Spelling Bee and has good lists at:
http://myspellit.com/ Sometimes we play "Stump the grown-up" and then DS6 gets a chance to read the words which are frequently pretty high-level for him, and DH or I spell them.
They have some games at:
http://www.merriam-webster.com/spell/index.htm and
http://www.wordcentral.com/games.html DS6 and DS8 enjoy these resources when they're in the mood for spelling.
HTH
