Web application Readability turns a website you’re reading from this:
Readability eliminates some of the common complaints about online content (poorly used colors, long running texts across a page) by reformatting the current page you’re browsing into a neat, black-on-white newspaper like column for easy reading with a click of a button (via a bookmarklet). You can also tweak the look-and-feel of the reformatted page to your liking.
You can check out Readability here.
Another tool that does more or less the same thing is Readable, with a lot more options but a bit less elegant looking.