Revive Old Post
This one is definitely one of my favorite WordPress plugins. Revive Old Post helps you to keep your old posts alive by sharing them and driving more traffic to them from social networks, automatically. There are lots of options that you can set, such as time between two automatic posts, categories or posts to be excluded, etc.
Revive Old Post is also available in a pro version with lots of interesting extra features: include hashtags and images, post to multiple accounts at once, custom schedule, and a lot more.
Free download: Revive Old Post
SEO Smart Links
A great way to link back to other posts and maximize your page views, SEO Smart Links can also be used to automatically insert affiliate links on selected words or sentences.
Free download: SEO Smart Links
Created by ElegantThemes, Monarch is a premium plugin that displays links to share your content on various social networks such as Facebook, Twitter, Google+ and a ton more. Monarch is very lightweight, fast to load and can be fine tuned to fit all your needs.
When it comes to driving traffic to your blog, search engines are definitely the best. A post ranking on top of the first page of Google for a given search term can by itself be responsible of 10% to 30% of your whole traffic. WordPress is good for SEO by default, but Yoast SEO can do wonders by helping you to optimize your content for search engine optimization.
Disqus in an external commenting system offering many advantages: it helps reducing spam, it can display ads that will get you some money, and it also has strong community features that can drive more traffic to your blog.
While Disqus will not make wonders in terms of traffic, it offers many advantages as discussed before, so why not give it a try and enjoy a little more traffic?