I use FireFox with add on spelling checker and it works with forum replies.
Contest (isn't that the "I am cool" smile)?! ...I like contests! Oh yeah, well I use Konqueror and it has integrated spell checking.
Besides doesn't Firefox have built-in spell checking (So should you really be using the `I am cool' smile if you installed an add-on for something that is built-in)?*Insert: "I am teasing" smile here*