Display a default thumbnail for posts with no specific thumbnail set using the new functionality (the_post_thumbail() function) in wordpress 2.9
WordPress 2.9 added support for post thumbnails but you have to set the thumbnail for each post you want to have a thumbnail. If your site already has hundreds of posts adding a thumbnail image for each post will be a lot of work even if you only want the same image for each old post.
This plugin allows you to specify a default post thumbnail that will be displayed for posts that doesn't have a thumbnail set.
This plugin requires that you have enabled support for post thumbnails in your theme