I have started to use a couple of apps on OS X that don't have built in support for spell checking (FireFox, TextMate). So, I decided to put together a simple spell check application, named SpellMe. Here is a screenshot:
You can download the application here.
Note : Only tested on OS X 10.3.5
The app is free, but if you end up using it, send me a postcard.
USE AT YOUR OWN RISK.