ajit prabhakar

This is simple volunteer registration plugin. 
The User will appear in Users menu. After login user can edit their profiles. 
USE echo do_shortcode( ‘volunteer_registration_form’ ); in template and theme. 
USE [volunteer_registration_form] in pages and posts.

Volunteer Registration

Simple Plugin

This is simple volunteer registration plugin.

Meitar

digiacom

Display and manage volunteer projects for any purpose.
<ul>
<li>Registers custom post type <code>wp-vpm-projects</code></li>
<li>Registers metaboxes to the editing screen for project meta fields</li>
</ul>
This plugin is in beta, and is not yet appropriate for a production site.
Important features like post ordering and administrative settings are absent.
That said, perhaps you will find it useful!
This plugin is in use over at <a href="http://www.volunteerwild.org" title="Conservation stewardship in Durango, Colorado" rel="nofollow ugc">Volunteer Wild</a>

WordPress Volunteer Project Manager

Display and manage volunteer projects for any purpose.

Volunteer Registration vs WordPress Volunteer Project Manager