Well, I do agree that you will never find scientific evidence for the Secret. It isn't science, but it incorporates scientific elements to appease the scientific minded folk of today.
It is metaphysics, and it is esoteric mysticism. It demonstrates the law of Karma - even every thought has an effect that will manifest. Is it really that ridiculous? If I unconsciously keep imagining how bad a job interview is going to go in my head, can I really be surprised when i am nervous and don't present my self well? If I keep telling myself I am a bad person and harbour irrational guilt (for example), I am affecting my future self in all sorts of profound and negative ways.
That is what the secret is about. How by thinking positively today, tomorrow you feel more motivated and do one thing more thing, like go to the gym. Eventually 6 months down the line your subconsciously programmed in a more positive way - more happier states, more confident - and the results will show in your life. It is simply a warning that what you are thinking is important, mixed with how to be mindful i.e. aware of what you are thinking.
Or at least thats the way I see it. The science bit is dubious, but either way it doesn't take away from the message above. And the religious side of it - not a fan of that either. But they do charge money and seem to run it like a business - and I don't think theres anything wrong with that. Its the spiritual new-age hippy connotations that you are annoyed with maybe, and don't blame you for that.