One very fundamental free online marketing tool is the Google Keyword Research Tool. Regardless of what kind of selling you do online, you will need to connect into the keywords that have relevancy to your business. You may use these keywords in your blog, web site, pay-per-click adverts, articles, videos, and any other kind of selling that you do. And the free Google tool permits you to find the precise keywords to target in your promotions--for free. Simply type in a word or phrase relating to your business, and the tool will supply you with a listing of all related keywords that folk are typing in, how many people are typing each term, and how competitive the terms are (how many other promoters are using them in their promotional efforts).
Videos are another very potent, and free, way to promote your business. All you need is a web-cam or a digital camera, and one to ten minutes of time to make a video. Simply upload it to YouTube or any of the other video sites, write a description of what you are talking about in your video ( make sure to include the right keyphrases ), and include your link, and you've got a magnet for folks who are searching for whatever it is you are speaking about or demonstrating on your video.
As you can see, there is more than just one free web marketing tool you can use to promote your business or affiliate products.