The New Age idea of positive thinking is an old standby in the field of self-help. Books on positive thinking have made bestseller lists for years, and the latest of these is The Secret by Rhonda Byrne. Having only read a synopsis of the book I can't really comment on its quality except that it is popular enough to put up good sales numbers. The essential idea of this book and others has been around for a long time. It proposes that according to the "Law of Attraction" our thoughts tend to become our realities, so in order to create good conditions in our lives we should visualize the conditions that we want to experience so that they can manifest.
So is this magick? Of course it is. Ritual magick is predicated on many of the same ideas, it just works a whole lot better than simple visualization.
[UPDATE: Newsweek just came out with a bit of a slapdown of the book recently. Their basic criticism is that, first of all, it's nothing new or even especially profound. Second of all, by claiming the the law of attraction "always works" the potential for blaming victims for their situations and yourself for your own failures is very high. It frustrates me when people make ridiculous claims for magical techniques such as implying that they are always successful. Magick gives you a solid statistical edge, but even if you cast a spell very well and have a lot of magical power you still can't guarantee success.]
This is not to imply that positive thinking is worthless. It is more like a good first step, in that most people will see some improvement in their lives if they focus on having an upbeat attitude and keep their mind open to new opportunities. What most of these books are short on, though, is the mechanism behind those improvements. In most cases, while the changes practicioners might seem paranormal in nature, operant magical effects are really more the exception than the norm, since the underlying mechanism is usually psychological in nature. This still may be thought of as magick in that it is change in conformity with will, but for most people the process by which desired changes are accomplished lies firmly within the microcosmic realm of the mind.
There are three ways in which this sort of practice can work. The first is related to Robert Anton Wilson's idea that "what the thinker thinks, the prover proves" discussed in Prometheus Rising and Quantum Psychology. Human beings usually notice only a small percentage of the information that they are receiving from the outside world. Rather than trying to process everything all at once our brains have evolved the ability to pay attention to only "important" information. Wilson recommends the experiment of spending a day expecting to find quarters on the sidewalk. You usually will find at least one or two if you are in an area that gets a lot of foot traffic, but without the expectation held firmly in mind you are likely to miss them. If you expect to come across fulfilling opportunities and train yourself not to dismiss them out of hand, you are much more likely to notice them when they come along.
The next way in which this practice can work is that your body language tends to mirror your thoughts. Skilled actors and confidence artists can learn to suppress this natural relationship, but mastering this process is difficult. You can usually safely assume that the people around you can perceive what you are thinking, at least to a degree, simply through their own unconscious interpretation of your body language. The bottom line here is that people like to be around others who exude confidence and happiness. Such people are just pleasant to deal with, as opposed to "psychic vampires" who actually have no paranormal powers but are nonetheless tedious and negative enough to make most people feel drained after dealing with them. By maintaining a positive outlook, you send out the kind of unconscious signals that other people want to be around. Since most success in life is predicated on other people who know and like you, this is especially effective when combined with an open mind that is always on the lookout for new opportunities.
The third way in which this practice can work is the creation of operant magical effects. People who fail to make positive thinking work usually make the mistake of discounting the power of the first two ways in which the practice works in favor of expecting magical effects to appear out of nowhere if they can manage to visualize hard enough. This, however, is quite difficult to manage unless (1) you are a trained ritual magician who maintains a regular schedule of spiritual practices or (2) you have a very high level of magical aptitude, which is as rare as any other heightened ability. The sad part about this is that some New Age self-help books are written in a manner that implies you just need to visualize hard enough and all your dreams will come true. The inevitable conclusion is that if your life is unsuccessful you just haven't been wishing hard enough, so in a sense your problems are all your own fault.
The truth is that ritual magick would never have developed as a discipline if simple visualization worked just as well. What would be the point of elaborate ritual structures and years of disciplined practice? In fact, ritual magick is a collection of techniques that allow thought to create reality in especially efficient and effective ways. A ritual procedure is a way of tuning the mind to a specific idea and that idea alone, in order to focus all of the energy of thought upon a single point. Engaging the bioenergetic centers of the nervous system empowers this single-pointed thought, transforming it into single-pointed will. Finally the magical link, a concept completely absent in most of the available positive thinking schemes, allows that single-pointed will to connect with its target in the material world and create a real change external to the magician. This process does not happen automatically, but is instead developed and cultivated in the course of disciplined practice.
The positive thinking crowd has a lot to learn from ritual magick, but the stereotypical dour ritual magician can also learn something from the positive thinkers as well. Thinking positive thoughts is not necessarily sappy or silly, and an upbeat attitude is not incompatible with a serious approach to practice. Similarly, directing some attention to more mundane opportunities is not necessarily a deviation from the spiritual path. In my experience a materially successful life supports a successful spiritual and magical practice. As above, so below.