I have recently signed up with suite101.com as a contributing writer. The purpose of the exercise is to get feedback on my writing. They have a reputation in providing advice to improve your writing (probably only from the SEO perspective). You first have to apply and submit sample articles. When they have accepted you, they'll give you some guidelines to follow to make your writing more searchable. Writers are instructed to kjeep these guidelines to themselves as their in-house secrets. Hence, I am not describing the details in here. Your first article will be reviewed with suggestions made, even repeatedly, by one of their editors before it's deemed publishable. I went through all that and finally had my first article published 9 days after I first submitted it. I searched the keyword tags on Google today and was really amazed to see the linking page to my article appearing as the first item on number one of the search results. (You can see the search results here)

Was this a pleasant accident?
I had previously published different versions of this content on hubpages, associatedcontent and ezines. These earlier versions somehow got loss in pages of Google search results. This experience seems to me an evidence that their guidelines and editing, probably together with the way they lay out their website, work well for search engines. For the purpose of improving your SEO skills and exposure to search engines, I think it's worthwhile giving them a try. However, they only accept around 20% of their applicants who can submit sample writings in the style of objective journalism rather than subjective blog writing. You'd also have to prepare to publish 10 articles in 90 days, otherwise they de-register you. Another thing you'd have to face is handling suggestions and flags to change your writing (which can be damned good as it is, to you). Some writers are apparently very happy with their income and experience there. Give it a go if it sounds like your cup of tea.