This plugin automatically converts keywords in a post title to tags upon saving. It includes a user-editable list of words you want the plugin to ignore, which by default includes the more obviously-useless words like “I” or “wasn’t.” You can also reset the list back to defaults by checking a box in the config page.
* Converts keywords in post titles to tags
* Includes user-editable list of words to be ignored
* Ignore list can be reset to default at any time
* Converts on save, not publish.
* Does not convert if there are already tags assigned.
WPMU adminstrators take note: this plugin is especially helpful if you’re
building a community-based site where tagging is important and your bloggers are
not always diligent about tagging.
Titles to Tags plugin for wordpress