Convert Text Files is a free wrapper Automator action for the textutil tool that will convert any text file of the types Plain Text, Word (Doc and WordML), Rich Text, HTML and Safari Webarchives into any other type.
The Convert Text Files Automator action will pass on the resulting files for further processing.
Installation: Download the Automator action. You can either select "Import Action..." from the "File" Menu in Automator and choose the action file or manually move the action file to the Automator folder in your Library folder.
NOTE: Convert Text Files is licensed under a Creative Commons Attribution-ShareAlike 2.5 License.