I visited a church of scientology once for a college project. They weren't crazy, and some of their material was interesting and relevant. They've got these self-help programs they teach (for a nominal fee), and a lot of it is about helping people. The problem with Scientology, near as I can tell, is that some of them are REALLY crazy, not that all of them are.
Like any "religion"/self-help movement, there are of course some kind, normal people in Scientology who believe they are actually helping people and doing the world good.
However, those seemingly common-sense self-help courses that are sold to you at the beginning are a gateway to indoctrination intended to keep you shelling out more and more money while subtly altering your worldview to agree with that of L Ron Hubbard.
For example: The basic Scn course titled "Overcoming Ups and Downs in Life" seems to be a simplistic instruction on how to deal with things that frustrate you and hold you back in life.
HOWEVER, within this beginning course manual is introduced the Scientology concept of the "anti-social person", later known as the "suppressive person". The reader is told that these "anti-social people" want to hold him back in life and they will criticize any self-help attempts he makes because they are "insane" and want to keep the world down. One of the many examples shown of these "anti-social" people depicts them complaining about a group holding signs that say "keep kids off drugs", because only an insane anti-social would criticize a group that wants to keep kids off drugs, right? (ie: the Scientology rehab front group Narconon.)
So basically the whole point of the seemingly innocent "Ups and Downs" course is to plant the seed that critics of Scientology are "anti-social" and "suppressive".
You can find out more about the manipulative aspects of the Scientology "basic courses" here:
The Scientology "Training Routines" - supposedly improve communication, but actually train you to "blank out" your mind on command, as well as learning to harass people more efficiently.
Scientology's "Study Technology" (which they claim is secular and try to sell to public and private school systems)
PTS/SP Course delves more into those "suppressives" who keep you down -- and criticize Scientology (BEWARE - link to Scientology-owned site)
All this stuff grooms a person to accept L Ron Hubbard's re-definitions of basic words such as "ethics" and "knowing", plus lots of Scientology jargon and acronyms -- all at a price of course. Courses start at a relatively low $60-$80 each, but quickly climb into the hundreds and then the thousands as it is "discovered" that a person needs more "help" in life.
Interesting, easy-to-digest essays about the Scientology thought process can be read at this site:
http://askthescientologist.blogspot.com/