Is this ILLEGAL?

I gave my resignation to my previous employer VERBALLY on Dec. 4, 2006. I gave them WRITTEN notice the day after (Dec.5, 2006). They decided to let me go on Dec. 5, 2006. Is that legal? Aren't they supposed to let you finish working your two weeks? I thought that was harsh since the Holidays are coming up, so that leaves me in kind of a bind.