Facebook has a membership of about 220 million, which can grow membership of groups and causes into the millions. Some of them are really big.
1.1 After login you see a page like this:

1.2 Enter "groups" in the search box and another box with a small icon will appear. Click on it.

1.3 A page like this will then appear. Click on "Browse groups".

1.4 A page like this will appear with all the groups listed in sequence from highest membership to lowest membership. It will also show the different types and categories of groups on which you can click to view the different listings inside each category.

2.1 Follow the same procedure after login. Enter "causes" in the search box and another box with a small icon will appear. Click on it.

2.2 Hover the cursor on "Find Causes".

2.3 A Underneath "Find Causes" the box will expand so you can click on "Browse Causes".

2.4 Again it will be listed in sequence from highest membership to lowest membership. It will also show the different types and categories of causes on which you can click to view the different listings inside each category.

2.5 Investigate the groups and causes, which may be related to your web niches, by clicking on the group or cause name, where you will find the description and purpose of the particular group or cause.
3.1 After joining, see on what aspects they allow you to make a contribution. It may be in the form of writing on a wall, adding a link, adding a topic or video.
3.2 Adding a link works wonderful, if you do it right. a.) Prepare a web page with images and upload it to your web site. b.) Shorten the URL link at tinyurl.com. c.) Enter the tiny url as a link on the group. d.) Facebook will look up the title and description in your meta tags and give you a chance to add some comments, as well as a chance to select the image you would like to be displayed.
3.3 a) Offer a free product or free advice, which can support the purpose of the group or cause, but at the same time give visitors the opportunity to obtain more information or products if they subscribe to your list.
or
b) Put the free product or free advice on a page where you are selling another product, giving visitors the opportunity to see it also.
or
c) Combine both methods.
Example one: I am posting links to a web page, with this product on display, on Christian/Religious related groups and causes, where I capture subscribers for more products or advertise another product as well:

See the page here.
Example two: I am posting links to a web page, with this product on display, on Parenting and Self-development related groups and causes, where I capture subscribers for more products or advertise another product as well:

See the page here.
You can make money by providing a suitable description and a link with your affiliate ID embedded, to a product of someone else you are promoting for commission.
The big benefit of starting your own group or cause is that you can then send out messages to all the members in bulk.
Do it with a link to also embed an image like in groups and causes above.
If you need some products to exploit the groups and causes, you can find many free products here.
9. We have so far started the following groups, which you can also join: