plain-template.php

<?php
if( is_single() ):
    $linebreak = "\n";
    header('Content-type: text/plain; charset=utf-8');
    if (have_posts()):
        while( have_posts() ): the_post();
            $content = wptexturize($post->post_content);

            //Ensure there is plenty of space above and below headings so they stand out.
            $content = preg_replace('/(<h\d>)/i', "\n\n$1", $content);
            $content = preg_replace('/(<\/h\d>)/i', "$1\n\n", $content);

            the_title();
            echo $linebreak;
            echo 'Published ' . get_the_date();
            echo $linebreak;
            echo $linebreak;
            echo wordwrap( strip_tags($content), 80, $linebreak );
            echo $linebreak;
            echo $linebreak;
            echo 'HTML version available at ' . get_permalink($post->ID);
        endwhile;
    endif;
endif;
?>