I was working on a website — needed a way to edit the “excerpt” of a page (as opposed to a post), but the theme I was using didn’t let me! So I wrote a very simple plugin to wrassle it into submission. It is now available on this site, free to anyone.
I’m not sure whether I’ll submit the plugin to WordPress.org, but you can download Torknado Page Excerpt from here and upload it to your site according to the instructions.
A little background: This excerpt is normally only visible when the page is listed as part of a list or grid on another page — most commonly, in the list of search results when someone does a search on your site. The plugin page discusses other cases where it’s useful.