In these day of firefox’s built in spell checker, why do we need an extra spell checker, well frankly for me its because Flex does not have one built in, enter
Spelling Plus by http://gskinner.com
Its the best spell checker i have found for flex, you do have to remember to manually ‘refresh’ the checker with code if you change text boxes via back end code (not the apps fault), but otherwise an excellent checker, and one I’m very happy with (be warned its not free)