Typepad (blogging platform) lets its users customize the size of the text-editing space with "Bigger"/"Smaller"controls at the bottom of the text box (click to see full-sized image).
The size settings are saved when you save a post.
Though there are other customization options available by clicking a "customize this display" link, I like how they've pulled out probably the most useful customization right on the page. This way, people who generally create short posts can easily have a compact editing space that meets their needs, while people who usually create long posts can work with a long text box.
