This plugin enables you to select which widgets appear on specific posts, pages, categories,author’s posts and tag pages. By default, all widgets appear wherever the sidebar is loaded within your theme. With this plugin, you can configure where widgets are displayed on a per post or per WP Template(Using conditional Tags) basis.
You can check out a presentation video at http://www.youtube.com/watch?v=m0h9_JXmXMc&e
This is the second release, the first release v1.0 being released 3 weeks ago. Within those 3 weeks i got lots of feedback and decided to release v1.2 with bugs being fixed and cool feature additions.
Check the official release post and download at -> http://www.thaslayer.com/2008/11/08/slayers-custom-widgets-v12-wordpress-plugin-finally-out/