Excerpt Editor provides a convenient place for creating and editing all of your excerpts. It can also add custom excerpts for pages (not possible without a plugin). This update contain two new features: auto-creating excerpts when publishing new Posts and Pages and displaying customisable excerpts from the content for posts without an excerpt. These excerpts are used in the RSS feed and also can be displayed on the Home or Archive pages (depending on the Theme). Currently the interface is only in English, but the excerpts can be in any language supported by WordPress.
WordPress Excerpt Editor, WordPress, Plugins, WordPress Plugin