Some of you may already know this but for those that don't,
Soy flour and soy isolate had the highest content of isoflavones and proteins, although 1oz isolate has 90g protein which is pretty powerful, here is the chart of different soy foods: http://soyfoods.com/nutrition/isoflavoneconcentration.html)

source: http://www.healthbulletin.org/soy/soy1.htm
The following are foods with the richest concentration of each of four phytoestrogens with the highest listed first and on down the list: Soy Flour, soy nuts, imitation bacon bits, textured vegetable protein (in soy burgers,) tempeh. (a fermented soy product,) soybeans, miso soup.

The following foods were rich in other types of phytoestrogens: These were not listed in order of amount of content, unfortunately: Apples, dried beans, tomatoes and juice, cauliflower, brussel sprouts, broccoli, potatoes, tea, strawberries, plums, pizza, dark bread, onions, green pepper.


Source: Wiki
Phytoestrogen
Main article: Phytoestrogens
Soybeans contain isoflavones called genistein and daidzein, which are one source of phytoestrogens in the human diet. Because most naturally occurring estrogenic substances show weak activity, normal consumption of foods that contain these phytoestrogens should not provide sufficient amounts to elicit a physiological response in humans.[citation needed]
Plant lignans associated with high fiber foods such as cereal brans and beans are the principal precursor to mammalian lignans which have an ability to bind to human estrogen sites. Soybeans are a significant source of mammalian lignan precursor secoisolariciresinol containing 13–273 µg/100 g dry weight.[41] Another phytoestrogen in the human diet with estrogen activity is coumestans, which are found in beans, split-peas, with the best sources being alfalfa, clover, and soybean sprouts. Coumestrol, an isoflavone coumarin derivative is the only coumestan in foods.[42][43]
Soybeans and processed soy foods do not contain the highest "total phytoestrogen" content of foods. A study in which data were presented on an as-is (wet) basis per 100 g and per serving found that food groups from highest to lowest levels of total phytoestrogens per 100 g are nuts and oilseeds, soy products, cereals and breads, legumes, meat products, various processed foods that may contain soy, vegetables, and fruits.[44]
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Hi Double_Ace,

Great compilation of information regarding the potency of soy. I know many women use soy and have no problems from it, but I felt it necessary to also contribute a warning regarding soy - especially soy protein isolates.

Soy can create several issues for health. Here are some websites that reveal some of the 'dark side' of soy usage:


http://www.electroherbalism.com/Naturopathy/Therapies/Diet/Soy/ProblemswithSoy.htm

http://www.utne.com/2007-07-01/Science-Technology/The-Dark-Side-of-Soy.aspx

http://www.mercola.com/article/soy/index.htm

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If you have low thyroid output or it runs in your family then steer clear of soy products. If you begin to have low thyroid symptoms and are using soy then stop using it. If you are estrogen dominant then don't use soy products.

If you use soy products then use them wisely. The idea is not to get the most soy into your body, but to find the dosage that produces the results you seek. Remember, use the least possible amount of any herb - more is not better - more can stop all results and make you ill.

Keep your health uppermost in your mind. Do nothing that would interfere with your good health... it is priceless beyond words.

Best wishes,
waxingmoon