This can add/edit excerpts for both posts and pages and would be more useful for sites that mainly use pages (use WP as CMS) or when there are a lot of posts/pages without excerpts. It can “auto create” excerpts using the first 40-55-70-100 words from the content.
Tested on WordPress versions 2.0.9 and 2.1.3.
You can activate it, edit/create excerpts and then deactivate it, minimizing any possibility for conflicts with other plugins that manipulate the excerpt.
Feedback is welcome.