I read Neil Jenkins' article Expanding Text Areas Made Elegant in A List Apart last week and was impressed with his technique.
Here's a link to the article: http://www.alistapart.com/articles/expanding-text-areas-made-elegant/
I decided to throw together a quick jQuery plugin to help spread the love.
It supports all reasonably modern versions of Firefox, Chrome, Opera and Safari and IE8+.
Let me know what you think. If you have any issues/feature requests, feel free to open a ticket on GitHub.