Redirectify

This plugin will redirect visitors to an alternative post / page or external URL when they attempt to view the specific post / page. The redirect will only happen when the post / page is viewed by itself, post content and other post data such as excerpts will still appear on the homepage and archives. This is an easy way to give permalinks to pages that are outside the control of WordPress and integrate them into your site structure.

This plugin adds a custom form field just above the submit box (where the publish button is shown), the value of this field should be the URL to redirect when that page is viewed.

Can we have an example?

Say you already have an external gallery not controlled by WordPress and you want to include a link to it using the page functionality of WordPress. By using this Plugin, the page redirecting to the external Gallery will appear in your page menu (wherever that is on your site, typically in your sidebar) and when a user clicks it (accesses the permalink in the address bar) they will be redirected to your gallery, wherever that happens to be.