Beej

In WordPress, attachments default to having their own pages. Sometimes, 
this is not desirable, as in search engine results. Use this small plugin to 
redirect your attachment pages to the post parent using a 301 redirect 
(post parents are also searched for by post name). If an attachment parent post 
cannot be found, it redirects to your blog home page with a 302 redirect.

Attachment Page Redirect X

Redirect attachment pages to their parent page (301), when possible, otherwise to the blog home page (302).

willshouse

Easily redirect any post or page to another page with a dropdown menu or by manually typing in a URL. Check out the screenshots. This plugin also changes permalinks and menus to point directly to the new location of the redirect – this prevents bots from getting a redirect and helps boost your SEO.
<h3>Description and Use</h3>
Simple redirection from pages or posts with an easy to use menu.
<ol>
<li>Edit the page, post, or custom post type you wish to redirect from.</li>
<li>There is a dropdown menu in the right hand column</li>
<li>Choose where you want to redirect to and save the post / page</li>
</ol>

Redirect

Easily redirect any post or page to another page with a dropdown menu or by manually typing in a URL. Check out the screenshots.

Attachment Page Redirect X vs Redirect