Transparent Corp's Research Area is arguably the most comprehensive resource for collated brainwave entrainment research.   Update: the main research area on Transparent Corp's website is currently being updated, so it is offline.  However, you can still access their peer-reviewed research paper as a PDF here: “A Comprehensive Review of the Psychological Effects of Brainwave Entrainment“.
One ounce of the buttery nut packs 11% of the daily recommended value of zinc, an essential mineral that may help reduce anxiety. When researchers gave zinc supplements to people who were diagnosed with both anxiety symptoms (irritability, lack of ability to concentrate) and deficient zinc levels over a course of eight weeks, the patients saw a 31% decrease in anxiety, according to Nutrition and Metabolic Insights. This is likely because zinc affects the levels of a nerve chemical that influences mood. If you're already getting enough zinc, then it may not help your mood to chow down on cashews (or other zinc-rich foods like oysters, beef, chicken, and yogurt). But, cashews are also rich in omega-3s and protein, so they're a smart snack no matter what.
Deep relaxation is another major benefit resulting from the brains cortical frequency following response while using brainwave entrainment. As the brain tends to mimic the rate of frequency it is exposed to, thus allowing it to enter into that brainwave state, this helps explain why this technology can produce benefits commonly found with meditation.

I believe that there is a frequency at which a brain functions, they can vary depending on circadian rhythm or other factors. You can check the various effects on the brain caused by varying frequencies. Check this link -> Binaural beats. When we expose our brain to isochronic/binaural beats, it has a resonating effect on the brain, i.e. the brain starts to alter its frequency in order to synchronise with the tone. Once the specific frequency is achieved, you will have the desired effect (depending on the specific frequency you are trying to induce).
It has been both a pleasure and an enlightening experience listening to the Equisync II CDs for the past month. As a 15 year stroke survivor, daily meditation has become a part of my life. Listening to these CDs reminds me of sitting alone in a forest during periods of rain, whether they be light, heavy, or in between. I am able to access my right hemisphere more readily and experience the feeling of nirvana that we all have within us. When I reach this point, my system reminds itself of all the compassion and connectedness we each have.
So using the example track above, the right ear is sent a 20Hz beat, compared to a 10Hz beat in the left ear.  As the right ear receives the higher frequency of beat, this works to increase the speed of the ‘left' brain hemisphere, which can be helpful for people with conditions like ADD, who are often found to have an abundance of slow wave activity in the left brain.
Just as stress can increase the risk for chronic diseases and other health problems, dealing with chronic conditions and poor health can increase the amount of stress one experiences. Stress also influences behaviors that affect health. Diet choices, sleep habits, and drug use are behaviors that are often negatively affected by stress (3). The APA’s 2011 survey showed that 39% percent of respondents reported overeating or eating unhealthy food because of stress, and 29% reported skipping a meal (3). In addition, 44% reported lying awake at night because of stress (3). On a positive note, 47% of respondents reported walking or exercise as a way of managing stress (3).
However, yoga and meditation take time to learn and master, and until the student becomes proficient, progress can be slow and frustrating, leading many people to abandon the effort before they see the benefits. Brainwave entrainment has the potential for helping a person enter the relaxing and rejuvenating mind-states brought about by yoga and meditation without the learning curve and time needed for mastering these other techniques. Brainwave entrainment may even facilitate learning other mindfulness methods by helping a person achieve success faster and more reliably. 
This is probably the most popular choice of frequency. The theta state is a state of tremendous stress relief. The benefits associated with theta level relaxation include improved concentration, reduced hyperactivity and improved memory. While in a state of theta relaxation, one’s blood pressure, breathing and heart rate all slow to a much more restful and healthy level that promotes natural healing. During theta relaxation one may also experience vivid flashes of mental imagery as the mind opens to memories or subconscious information that is not available to the conscious mind during the normal waking state. The theta state is a very deep state of relaxation that is excellent for deep hypnosis and mental programming.
In much the same way, Christian fundamentalism is a parasitic ideology that inserts itself into brains, commanding individuals to act and think in a certain way — a rigid way that is intolerant to competing ideas. We know that religious fundamentalism is strongly correlated with what psychologists and neuroscientists call “magical thinking,” which refers to making connections between actions and events when no such connections exist in reality. Without magical thinking, the religion can’t survive, nor can it replicate itself. Another cognitive impairment we see in those with extreme religious views is a greater reliance on intuitive rather than reflective or analytic thought, which frequently leads to incorrect assumptions since intuition is often deceiving or overly simplistic.
Going deeper now, spiraling downwards, you enter “Into the Vortex.” Imagine now you are standing outside the Pyramids of Egypt and a hot wind is blowing by. Wind can be heard with deep, spatial synthesized drone sounds. This recording actually DOES take you what has been described as the “Pyramid Frequency” the frequency that has been said to resonate outside the great walls of the Pyramids in Egypt. This CD will take you down to even deeper brainwave frequencies than the first CD …. 9.41 Hz to 7.8hz
The Brain Salon collection is the culmination of more than 100 years of brainwave research that has discovered how to help the brain switch mental states in a matter of minutes. Brain Salon is a collection of six different audio CDs that use special inaudible pulses with lavish natural sounds and special entrainment techniques like binaural entrainment, sound modulation, and isochronic tones to influence brainwaves. The six different discs are designed to help listeners relax, feel creative, achieve deep sleep, reach high energy levels, be in a more positive mood, or achieve razor sharp focus in less than 30 minutes. In addition to the full audio series, customers will also receive the complete Brain Salon user manual, lifetime support for Brain Salon products, a total money-back guarantee within two months, and a bonus MP3 recording of Craig Tice, original Brain Salon developer. All of the materials are available online only for two monthly payments of $77, or a discounted one-time payment of $127.
By exposing the brain to special computer generated tones that are pulsed at a specific rhythmic frequency, the brain will synchronize its own electrical impulses to that same frequency. This means the brain becomes "entrained", or matched, to the specific frequency of the pulses, which gives you the ability to choose the primary frequency you want to experience in your brain. By guiding the brain into deeper (slower) frequency brainwave patterns, you can induce a profoundly deep state of relaxation and meditation with almost no effort.

An invigorating, brain-sharpening session, this audio starts at 14Hz, a beta feel-good frequency, and SR harmonic. It then steps up in six-minute harmonic increments, gradually up to gamma 39Hz, leaving you feeling mentally stimulated and full of energy. A binaural beat track supports the main frequencies for those wearing headphones. Uplifting background music with embedded amplitude modulation provides a further layer of entrainment. Excellent for use as a morning alarm clock, ahead of a big night out, or to inspire those tired trips to the gym.
These guys behind this system are just brilliant, and I have seen many people confirming this, as they are loving the experience with this system. Actually, I went through a few groups and forums and found people saying they had a pretty great time. But since I’m not allowed to take screenshots of the forums, here is one I managed to get elsewhere:
The MP3 that starts it all. This has a ‘space like’ ambient sound that truly does deliver you to the Gateway and ready to be transported into another world. You can hear space like winds and deep drone sounds – perfect for meditation. Below, you will hear the Isochronic tones and binaural beats, taking you down from 12 Hz to 8 Hz and then ramping up again to 12 Hz to complete your journey.
Many of the long-term side-effects of menopause are associated with a deficiency in magnesium. These include heart disease, osteoporosis, weakness, weight gain, and feeling cold all the time. When you take a magnesium supplement, it can help relieve many of these problems and help your body balance your hormones. Magnesium can boost your energy by helping to convert the T4 thyroid hormone into the more active and bioavailable T3. It can also help the liver reduce levels of cortisol, adrenaline, and excessive estrogen.
A study by Tina Huang, PhD, and Christine Charyton, published in the September 2008 issue of the journal, Alternative Therapies examined the results of twenty previous studies measuring the effectiveness of brainwave entrainment for improvements in cognitive dysfunction and deficits, stress reduction, pain management, migraine and headache control, pre-menstrual syndrome, and behavioral difficulties, and all showed significant improvement in symptoms using entrainment techniques.
“Wow, wow, wow! When I coach people, the first thing I do is help them change their state as quickly as possible – and now it’s as easy as using one of the Brain Salon sessions. I can’t wait to share this program with all of my clients – once they use Brain Salon to easily get into a powerful state, then the work I do is going to take them to levels they never imagined possible…”