I love the Pew Forum! I was impressed (although not all that surprised) at how well atheists did. Mormons did particularly well on a lot of them, too. I got 15/15.
For those who don’t know about the Great Awakenings, there were four “waves” of religious revival throughout the course of US history. Although there were four of them, the first two are probably the most significant. All of them were evangelical movements in America that led to a dramatic increase in religiosity, church attendance, the degree to which people actively participated in religious activities, etc. Some of them were strongly associated with Tent Revivals, altar calls, and such. Some of these waves brought about dramatic changes in the way preachers preached, in that they stopped reading sermons (from a page in front of them) that were theologically complex and started a more expository style of public speaking that was designed to elicit an emotional response. It was also during these periods that a lot of new religious movements and denominations were formed. Most of the 30,000+ denominations that you keep hearing about owe their existence to one Great Awakening or another.
Funny thing is, these denominations were and still are largely non-sectarian, and the huge variety of denominations tended to appear during times of great religious health and vibrancy in America. Ever since the fourth one ended (around the start of the '80’s, although there’s some debate as to whether it actually was an Awakening), most Protestant ministers/pastors/church leaders in America have wanted to recapture this kind of thing. They also don’t tend to mind if new denominations are formed in the process, as they typically don’t come about in a sectarian kind of way.
Anyone who’s interested in knowing things about the plethora of denominations in America and the way it all began, read up on some of the Great Awakenings. America’s responsible for most of the Protestant denominations in the world, and the four Great Awakenings, in turn, are largely responsible for birthing the bulk of those.