From Stone Table Software:
RTF-to-Styled Text is a handy conversion utility which translates Rich Text Format (RTF) documents to ordinary Macintosh styled text files. Styled text documents can be opened by most word processors, including SimpleText and Z-Write.
The RTF format is sophisticated and supports features that styled text does not, such as text alignment and inline graphics. Extra formatting is simply ignored by RTF-to-Styled Text; all text translates fine.
Most word processor support RTF exporting, so you can use RTF-to-Styled Text as a way to transfer text from one program to another.
RTF-to-Styled Text's batch processing feature is ideal for converting numerous files.