Michael Henke

This plugin provides flattr-buttons for comments on your blog if the comment author entered his Flattr-ID. 
There will be an additional input field right below the comment text box. Alternativly you can input a piece of code in your theme to place the field somewhere more nicely.

Flattr Comments

This plugin provides flattr-buttons for comments on your blog if the comment author entered a Flattr-ID.

This plugin is including the Flattr button for your blog inside a widget. 
This way the button can be easily positioned in any of your themes sidebars.
Your flatter credentials are all automagically imported from the official Flattr plugin.

Flattr Widget

This plugin is including the Flattr button for your blog inside a widget.

Flattr Comments vs Flattr Widget