Peter Westwood

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.

PJW Page Excerpt

This plugin allows you to specify a specifc excerpt for WordPress pages.

Johan van der Wijk

The Recent Posts Widget Plus plugin allows you to display a list of the most recent posts from all or a specific category or tag. It not only shows the post title, but also an excerpt of the post.

PJW Page Excerpt vs Recent Posts Widget Plus