Spelling Cow: JS Spell Checker:

Spelling Cow allows you add a script tag, and spell check is enabled on your website. There are also some variables you can tweak too if advanced features are needed.

This means that you can add spell checking to your applications, but as the latest browsers have added inline spell check, is there use to it?

This is a neat tool and would probably be fairly easy to add…

(Via Ajaxian Blog.)