Check out http://collabedit.com/, http://piratepad.net/, http://typewith.me/, and there's a ton more over here - http://etherpad.org/public-sites/. I've been asked to use a collabedit, piratepad and etherpad (now acquired by Google) for phone interviews, they all work well.
I checked out piratepad, but it doesn't have syntax highlighting. TypeWithMe is a bit too heavy (took a long time to load on my computer). I really liked collabedit.
I liked codibility. I think I won't use it this time, because it might take a bit of time to prepare, but I will for sure use it the next time I am looking for a programmer.