Most are made by different companies, and can have several positive and negative attributes, so it's important to know which one might work for you. You may buy a supplement on a website, but not get a copy, and you can't order it directly from the manufacturer.
You can see a list of supplements and their reviews here.
The supplements on this page are not a complete list, and you can easily add more. If you have any suggestions or questions, feel free to ask. The most recent reviews in this section are on the newest products. The oldest reviews in the section have been added since then. The supplement companies are listed alphabetically, by name. The review links in the top-right of each company's reviews section go to the supplement's website, where you can also find more information about the product, a full list of ingredients, and product ingredients, and a list of the supplements' "best sellers." Most of the "top sellers" are low-cost supplements that are very popular among the "health-conscious" crowd. The best sellers will always have more than one of these ingredients, though, so this doesn't always mean it's a high quality supplement. Some companies may not even advertise on their own website or social media, and that's OK! In general, the most popular supplements are vitamin E, beta carotene, iron, and zinc.