On the new web project im working, i needed extra titles to be added to menu and blocks. A quick search on d.o return no results for block subtitle. so here goes a new project i created.

This module allows a user to add subtitle to blocks.

Installation

1. Enable the Block Subtitle module under Administer >> Site
   Building >> Modules
2. To add a subtitle to a block, go to the block configuration page. A new field 'subtitle' will be available. Enter your subtitle and click save.
3. Now you need to edit block.tpl.php in your theme. Add the following code to show the block subtitle :
   
   <?php if ($block->subtitle): ?>
    <h3 class="subtitle"><?php print $block->subtitle; ?></h3>
<?php endif; ?>

Demo

Check out the blocks on the sidebar of this page.

ok let me have your feedback on this and how we can improve the module.