Localize URL bases

This should cover everything:

function wpa_rewite_translate(){
    global $wp_rewrite;     
    $wp_rewrite->pagination_base="pagina";
    $wp_rewrite->author_base="autor";
    $wp_rewrite->comments_base="comentarios";
    $wp_rewrite->feed_base="alimentar";
    $wp_rewrite->search_base="busqueda";
    $wp_rewrite->set_category_base( 'categoria/' );
    $wp_rewrite->set_tag_base( 'etiqueta/' );
}
add_action( 'init', 'wpa_rewite_translate' );

Feel free to laugh at my translations, haha.

Also, to flush rewrite rules when your theme is activated, add this:

function wpa_flush_rewite(){
    flush_rewrite_rules();
}
add_action( 'after_switch_theme', 'wpa_flush_rewite' );