The mainstream of life.
Ideas that are in accordance with commonly held beliefs in a society are an example of ideas that would be described as mainstream.
The collective body of beliefs of the U.S. citizens are an example of the American mainstream.
They often carry stories you won't find in the mainstream media.
Mainstreaming has become more common in recent years, as studies have shown that many mainstreamed students with mild learning disabilities learn better than their non-mainstreamed counterparts.