Steve

This plugin uses custom fields to allow the page title tag to be customised and differ from the actual page title.
Both meta descriptions and keywords can also be added if required.
Page meta details can be modified on any publicly accessible post type, such as posts and pages, as well as custom post types.
Theme and plugin developers should note that it is possible override the page title within your templates by setting <code>$wppm_title = 'Newly defined title';</code> before the call to <code>get_header();</code>.

Page Meta

Adds the ability to override the page meta title and add in meta descriptions and keywords for pages.

Kumbh Design Inc.

You can set meta tags like keyword, description. You can customize on each individual page/post as well.
<h3>Features</h3>
<ul>
<li>FREE Plugin.</li>
<li>One click to Install.</li>
<li>Simple and Easy to Use</li>
<li>Do not need to edit your theme’s core files.</li>
<li>Quick and supportive.</li>
</ul>

WP Simple Meta Tags

Allows you to set meta tags like keyword, description and you can customize on each individual page/post.

Page Meta vs WP Simple Meta Tags