Hello and thank you for the suggestion,
A couple of spell checkers exist that could be added to the forum. Unfortunately they are not very good. Spelling cow, which is one of the few good ones, has the disadvantage of placing google ads.
The best solution is to add a spell checker on your browser. The spell checker of google toolbar, as suggested above, is one of the best. It will do the job better than any forum spell checker and it will not have the drawbacks.
Here is the address for the google toolbar:
http://toolbar.google.com/
Nevertheless, If a lot of people feel that they need this feature I will add it.
Thanks.