If you're looking for resources on cults and other dangerous groups, try here:
The Ross Institute Internet Archives for the Study of Destructive Cults, Controversial Groups and Movements
I haven't experienced anything as severe as what you describe, but I did have an experience with a cult-like group once.
A couple of friends of my wife's recommended a 2-day seminar to us after they took it. The seminar title ("personal mastery") was rather vague, but seemed like it might be legitimate in a Dale Carnegie sort of way, so we went. The "seminar" used a number of tactics that set off alarm bells for me and (as I later found out) were listed as warning signs of a dangerous group. The course seemed to have two main aims:
- break the participants down emotionally and instill dependence on the group.
- get the participants to sign up for the next course, a week long and several thousand dollars.
I rejected the thing once I figured out what was going on. The friends who suggested the course still had a very high opinion of the organization, but eventually they drifted away from it. I guess a seminar every few months isn't enough to keep most people engaged, and eventually, most people will start to see through some of their lines (e.g.
"don't worry if you don't have the money for the course - with what you learn, you'll be able to pay for the course many times over. Just put it on your credit card, keep a positive attitude, and the money will come" - I'm quoting from memory, but that's pretty close to what they actually told us), so luckily, I never had to worry about "deprogramming" or anything like that.
I did worry about some of the people in the group who really did fall for the stuff, but I had no way to contact them after the end of the "seminar".