Article writing is a very easy, popular and cheap method to promote products and services over the internet. There are a lot of free blogging packages available on internet, you can use them online (as blogspot and wordpress) or you can download and install them on your domain (as wordpress). The first case is completely free, in the second case you have to pay the domain name reservation (and renewal if you have a limited reservation as .com, .net, .info TLDs) and the hosting.
Writing the text of articles and posting them on the internet takes some time (depending the subject and your experience), but once you set up a system it’s easy to do this task (or job) as often as you can. The content of your articles is a great method to improve the traffic of a website, even when they are on other websites (with the condition of putting backlinks to your site in the text).
The search engines will take into consideration the content of your articles as the uniqueness and how long is the text. Do not copy and paste other people articles or you will damage your reputation from both points of view: human and search engines. The websites and blog that reproduce content from other sites are being penalized or even blocked (in extrem cases).