WP Inline Edit - adds ability to edit your post/page from page/post itself without going to wp-admin edit page.
Live Edit - more complex than above - adds live edit function (with resizeable windows) for post titles, post content, thumbnails, files and custom fields.
Edit Flow - useful modular management plugin to organize work with calendar, comments, notifications and more.
AJAX Post Meta - allow any plain-text custom field to be edited via AJAX on the All Posts admin page. Quickly edit SEO titles, descriptions, keywords and more. Auto-detects popular SEO plugins and add appropriate columns.