Bing404 – Biggest issue with sites is that there can be dead links, a dreaded 404 page. Don’t waste that SEO juice, get Bing404 and it will provide search results from your blog or from Bing search engine.
Disqus Comment System – People can communicate quickly then you will get more traffic.
Efficient Related Posts – This grabs a bunch of related posts and publish it on the bottom of your post. This provides more links and keep your readers on longer which both is great for SEO. I’ve try a few and this one provides more relevant posts.
TweetMeMe – Shows the number of tweets and enable people to retweet your post. More links on twitter and more traffic, the better!