I have heard for the longest time that there was a built-in spell check for Firefox, which has fast become my browser of choice. But after a particularly long post in MonkeyFilter, and in dire need of spellcheck, I finally buckled under and looked around. It was a little hard to find, as I mistakenly used FireBird as a search term instead of FireFox (Thanks to Firesomething I'm writing this in Mozilla Firedog). But soon enough I found Spellbound, which includes right click support as well as an icon you can add to the toolbar. It's only been two days, but I am loving it.