My friend Joe has a website with stacks of articles he's written about Pentecostalism.
Pentecostalism has been one of the most influential movements of the 20th Century and is looking to be a global force in the coming decades. Where the church is growing most rapidly, Pentecostalism is very influential.
If there were two worldviews worth knowing a lot about in preparation for the future, they are probably Pentecostalism and Islam.
Joe has hundreds of people visit his site, mostly from America, and most Pentecostals, who really appreciate the site.