Prasanna SP

Just like the normal WordPress site feed, wordpress categories and tags also has feeds. The category feed is located at <code>site.url/category/categoryname/feed</code>. This plugin automatically adds the RSS feed link to the current post categories after the post content. By default the plugin shows category feed link on single posts. You can change it’s settings to show it on other pages, such as archives as well. You can change it’s title in WP-Admin –> Settings –> Follow Category Feeds.
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Follow WordPress Category Feeds

This plugin adds link for the category feeds after post content.

Skysa

Simply set the Twitter account you want users to follow; then, when they click the Twitter Follow button at the bottom of your site, they will start following your account on Twitter. You can optionally set to display your current followers count next to the Twitter follow button and also the language of the Twitter follow button text.
http://www.youtube.com/watch?v=Zj1uGXX2xrk&hd=1 
<a href="https://wordpress.org/extend/plugins/tags/skysa-apps" rel="ugc">More Skysa App plugins</a> -|||- <a href="https://wordpress.org/extend/plugins/skysa-official/" rel="ugc">Skysa App Bar Integration plugin</a>

Skysa Twitter Follow App

Allows your site visitors to follow your twitter account with one click, without leaving your sitet.

Follow WordPress Category Feeds vs Skysa Twitter Follow App