Seriously Simple Speakers: Rename the 'Speakers' label to something else. In this example I have renamed the 'Speakers' to 'Guests' in both the plural and singular instances - you can make those labels anything you want by editing this code and adding it to your theme's functions.php file or a functionality plugin.

functions.php

<?php
add_filter( 'ssp_speakers_plural_label', 'ssp_speakers_plural_label_custom' );
function ssp_speakers_plural_label_custom ( $label ) {
	return 'Guests';
}

add_filter( 'ssp_speakers_single_label', 'ssp_speakers_single_label_custom' );
function ssp_speakers_single_label_custom ( $label ) {
	return 'Guest';
}

// Changing the slug: 'speaker' to 'guest'
add_filter( 'ssp_speakers_taxonomy_slug', 'ssp_speakers_slug_custom' );
function ssp_speakers_slug_custom ( $slug ) {
	return 'guest';
}