Not expert in field US news stations. But have heard something good about Media Research Center - depolitices news. They have quite a lot projects Newsbuster is one of them. It needs a critical eye to evaluate whether MRC is actually objective.
Another source, yet unknown and unchecked, for news stations political sepctrum:http://www.journalism.org/interactives/media-polarization/table/distrust/
And something further to get you started:http://researchguides.library.vanderbilt.edu/policiesg-l/mediabias
We are all subjective, biased. Nothing bad about it. Take just topics of abortion, capital punishment etc. Our intrests and views are fundamentally different. We just need to take into considerations the news source and which way it tries to lead us. Approaching critcally to every fact, statement is a remedy-medicin reading any news. For example I tend to read The Economist - I know its West and slightly promotes liberal economy-politics. But its not bad because of its bias. Just must remember not to let one influence fully about it. The above picture were a real thing and is most commonly showed to paint a image how different media stations see things and intentionally purport the real state of things.
Second thing about bias is "missing out" or "leaving blank". For example not talking, writing at all to protect certain type of viewpoint. This is bias in deepest sense, because not even critical eye can detect it, if information is not shared. And for the last Cover stories are generally most biased - best way to evaluate what political spectre they promote or try to belittle.
When it comes Big topics - foregin policy, international affairs, diplomacy, defense, economy. I would suggest to leave out small daily news and try to get hands of reasearch centers. Not because they are least biased - but bias is more straightforward. Pointed out what view on supports. Everyday journalist can not be expert of those fields. Reasearch centers generally do not make common fallacies, that can be found in daily news. And peer-review is much strickter.