This plugin allows you to specify a specifc excerpt for WordPress pages.
The plugin adds an extra box to the set an Optional Excerpt for a WordPress page similar to the box which is available for posts. The box is aded using the dbx_page_advanced hook for versions of WordPress earlier than 2.5 and using add_meta_box() for WordPress 2.5 and later.
Te puedes descargar este plugin para utilizarlo en tu instalación autoalojada de WordPress.