Hello everyone. I created a WordPress plugin that automatically adds user-specified tags to posts when they are published or saved. Thanks to this plugin you won't have to manually assign tags anymore. You just have to create a list of tags and their related words and you are done, APT will handle the rest.
Screenshot: http://imageshack.us/a/img404/8614/automaticposttagger.png
Download: http://wordpress.org/extend/plugins/automatic-post-tagger
License: GPLv2 or later
Enjoy!