Look in Magazines for Libraries for short, descriptive articles about many major magazines, newspapers, and journals.
For Example:
"The Nation is a strongly leftist publication that includes original in-depth reporting as well as significant editorial and opinion content."
"National Review...is generally considered to be the premier mainstream conservative publication."
"The Monthly Review has been publishing articles from a hard-left perspective for over 60 years."
"The New American is a hard-right magazine (usually further to the right than the National Review), published by the John Birch Society in one form or another since the 1950s."