Hooking in to an archive page?

Use archive_template filter in your plugin to override archive templates for a given post type, for example, movies:

<?php
function get_movies_archive_template( $archive_template ) {
     if ( is_post_type_archive ( 'movies' ) ) {
          $archive_template = dirname( __FILE__ ) . '/templates/movies-archive-template.php';
     }
     return $archive_template;
}
add_filter( 'archive_template', 'get_movies_archive_template' ) ;

See archive_template in Codex.