I don't generally think of my own list as a traffic source, because those are people that subscribed and keep coming back, mostly because of good content. This is more tutorial about where to get fresh traffic from in case a person is not using some of these sources already. Where have you guest posted, I haven't seen any, would like to read some of those :)
Search engine traffic. Search engine traffic is that traffic that comes from visitors clicking on links on a search results page for any search engine — whether Google, Bing, Yahoo!, Blekko, or similar. This traffic source is divided into organic or non-paid search engine traffic — meaning that the visitor clicked on a so-called natural search result — and CPC or paid search engine traffic, which is the traffic you purchase (via pay-per-click ads_ from search engines. Search engine traffic usually indicates that you have good or at least reasonably good content. It also can mean that you have chosen a good software platform. Be sure to learn which keywords are driving this traffic. Multi-channel merchants, as an example, may find that their brand name is a key search term. When this is the case, offline marketing is usually the real traffic driver.
Referral traffic is the third most important source, bringing 8.3% of total traffic to the leading retailers’ websites. There are four online retailers that receive significantly more referral traffic than others: Amazon, Apple, Walmart, and Gap. Live.com is their leading referral source sending nearly 3% of traffic to these sites. Also, we see that Amazon often directs its visitors to Walmart , which brings this company 3% of its traffic. And Amazon itself receives most of its traffic from Amazon-affiliated sources such as Primevideo.com and Audible.com.
Google makes constant efforts to improve the search algorithm and detect quality content and that is why it rolled out the Google Panda 4.0 update.  What is this update really doing? It deranks low quality content and boosts the high quality one, according to Google’s idea of valuable content. In the screenshot below you can see what kind of content you shouldn’t be looking into if you are really determined in making a mess out of your organic traffic. 

Mobile traffic: In the Groupon experiment mentioned above, Groupon found that both browser and device matter in web analytics’ ability to track organic traffic. Although desktops using common browsers saw a smaller impact from the test (10-20 percent), mobile devices saw a 50 percent drop in direct traffic when the site was de-indexed. In short, as mobile users grow, we are likely to see direct traffic rise even more from organic search traffic.