I can't remember where I first saw this, probably over at Trents..

It's called ieSpell and it spell checks web forms that you've filled in. Like email, or a blog! I'm loving it, I've been wishing blogger had a spell check for a long time. You download it and it adds a button to your toolbar, where your print and history icons are, etc. Write your blog, hit the icon and bodda bing bodda boom, blog spell checker. It only work in IE of course, so if you're using a Netscrape, you're on your own. But [cough] why would you?