Webster's Speller: Absolute Favorite!!!!!! And it's free! Poke around this website, read and learn. Webster's Speller teaches children to read syllables, which in turn helps them to spell the syllables correctly. Excellent, by far the best reading curriculum around, IMHO.
Free Spelling site for the Presidents of the United States with a fun fact to go along with each president. You can also play a few games to help with spelling of their names like hangAbot, word jumble, spelling bee or word search.