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.

Kamal Hosen

pixelplugin

This plugin will easily give the user the option to follow the category or tag of his choice. This is basically a widget based plugin, it will work from the time you activate your tag / category follow widget after you install the plugin. One of the conditions for this to work is that the user must be logged in.

Follow Tags & Categories

User's can follow specific Tags or category and show only those tags/category posts.

Follow WordPress Category Feeds vs Follow Tags & Categories