We've never studied spelling either, and my kids do get tested on spelling every year when we do the CAT 5. They are always in the top 2%, even though we test "up" 2-4 grade levels. Every kid is different though, and if you really want a spelling program, you could try Spelling Power, which I have heard positive things about, or maybe look for spelling bee prep tools.
I think spelling is much less critical a skill to have these days, with spellcheck available on every computer. It's just icing on the cake, like nice penmanship.
