How can you possibly choose? For me, I think the most important thing is to just get started. You can learn NonDirective Meditation for free, and you can also pay anywhere from $8 to thousands to learn it - so what's the difference?
Well, there are a few different ways in which you can meditate that are still considered NonDirective meditation, yet they are pretty different - because to be considered "NonDirective" meditation they have to be not directed in nature - so in meditation, you're not focusing on anything in particular.
The price differences are typically based in how much support the course provides you in the long run, and the nature of the support. I think it is really important to get some support as part of the deal.
Our own (NonDirective.org) course is fairly inexpensive, yet we keep it updated on a regular basis, and we also provide support forums where you can ask us as well as your peers various questions you might have, and get group support.
In Transcendental Meditation, it's quite expensive, but you get access to teachers (in person) for the rest of your life.
Other courses provide no support after you read / take their course.
So it's important to choose a course that provides the right balance between cost and support for you - as well as choosing a course that you just "feel good about" - one that feels right to you.
You may want to choose one of the less expensive versions to get a taste of the methods, and then move on to something with a higher level of in-person support, if you like the technique, but feel that you need more of that in person help.
We're going to keep this site updated on all the different techniques, and of course we'll keep our own instructional course updated and current as well. We believe that the right type of meditation for one person may be quite different than the right type for another. Likewise - the right teacher / teaching arrangement may be quite different from person to person as well.
So look around, learn all you can, and then pick one that seems right for you - or one that seems to speak to you.
Every course we have on this site is legit - we have looked in to each of them well enough to know that there are good people who really want to teach and improve others' lives, so you don't need to worry about that. If you find it on NonDirective.org, you at least know that.
From there, just choose one that feels right to you!