You can edit text boxes, forum posts and many more text files using an external editor.
For firefox 1.x there is also editus but ViewSourceWith works with
Firefox, Mozlla, Seamonkey, and Thunderbird.
If you use a decent editor (not notepad) you can use it for more effective editing of longer posts
plus spell checking. Just save the file and close the editor and it will load it into the browser (may take awhile for larger texts). It can also be used for other file types ! Right click on the text field and go to view source with >
Man, I'm going to have to set up my vimrc file to turn on spell checking for forum posts !!
HOOOOOOOOOOZAZZZZAAAAHHHH and GOD bless the auther of that addon !