Every one know content is king of the all type SEO. If you have quality content you can attract anyone to visit your site and spend some time on it. Answer is where you can public your content and get back link for your site. Then I must say guest blog posting is one of my favorite way.
You can find many site during the search on all search endings. A huge list of informative blogs have their special offer for others as "Write for us" . You can publish your stuff on them and get a reasonable back link to your site. Before public your content on any sites just make sure the link must be "Do-Follow".
I am using guest blog posting last 4 years and its still working for me. I recommend this all of you.
If anyone have site for posting kindly share here with us.