The London newspapers provide a pretty good example of this. Each is more or less open about its own political stance, and as a result you can often pretty much determine the true story by reading both the Guardian and the Telegraph.

Also, political bias forms a sensible point of differentiation in the market, which enables the London market to support more competing newspapers than any other city that I know of.

Of the US news sources, Fox News is fairly open about their bias (there's an implicit nod and wink in their Fair And Balanced slogan), but the others seem to be hanging on to the illusion that they're unbiased.