This plugin allows you to add an ajax-updated countdown to your blog.
With this pluging you can add a countdown to your blog. Just specify an end-date in the settings (backend) and put one single line of php-code somewhere you want this countdown to be displayed. This plugin uses the ajax-technology for updating the countdown every second. The moment you change the specified date in the settings, the plugin recognizes this change and updates itself according to the new date.