WordPress.org

Lists all categories in a dropdown box and after selecting one the second dropdown box gets populated via Ajax with all posts from this category. You can use this plugin as widget (with some options) or just add the function to display the two dropdown boxes somewhere in your template files.

This plugin is especially good for content heavy websites and enables users to navigate quickly to a certain post.

Please use the comments at http://learn-thai-podcast.com/blog/ for support.