Occassionally I'll have someone post a comment that includes a URL. Wordpress automatically links to that URL, but often times it's too large for the alotted space. So depending on the browser, it might break it entirely. John recently wrote about a plugin that would fix that problem. WP-Chunk doesn't require much to work. There's no customization, or settings to change, it just works.

His example is of a long URL, but I imagine you could use it for any content that would cause the output of the post to expand out too far. And no configuration makes it even better!