I’ve just posted my first WordPress plugin, Keyword Tags, which adds keyword/tagging capabilities to WordPress. While many such plugins already exist as far as I’m aware this is the first to support the MetaWeblog API – meaning blogging tools such as Windows Live Writer or Ecto can publish keywords with no need to manually edit tags.
The plugin also offers the ability to automatically append keywords to posts for services such as Technorati or WordPress so there is no need to edit theme files. If custom behaviour is required the user may use the simple API to control the output and formatting of tags within their theme.
Read more and download it here: Keyword Tags for WordPress