As far as Guest posting concerned, it depends on your niche market. for instance if you are good at enhancing website user experience, then you can write a good article on user experience & offer it to a popular well known Blog in the related user experience niche. If your article is valuable to them, then they don't hesitate to add your link back to your website, thus giving you link juice along with referral traffic.
Almost all top blogs accepts guest postings. It's only a matter of finding list of blogs related to your "market theme".