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.

antonpug

This plugin adds a customizable Better Follow Button at bottom right corner of your Jetpack-powered WordPress.org site.
The plugins integrates with the built in subscription manager of the Jetpack Plugin to collect the email of the subscriber and handle distribution of new posts via email.
NOTE: This plugin requires the Jetpack plugin to be installed & activated
For further information visit the plugin website.

Better Follow Button for Jetpack

Adds a floating subscription button (like on WordPress.com sites) to Jetpack-powered WordPress.org sites.

Follow Tags & Categories vs Better Follow Button for Jetpack