<?php
// Prepends category name(s) to event titles
function tribe_events_title_include_cat ($title, $id) {

	$separator = ' &raquo; '; // Separator between categories and title
	$cats = get_the_terms($id, 'tribe_events_cat');

	if (tribe_is_event($id) && $cats && !is_single()) {
		$cat_titles = array();
		foreach($cats as $i) {
			$cat_titles[] = $i->name;
		}
		$title = implode(', ', $cat_titles) . $separator . $title;
	}

	return $title;
}
add_filter('the_title', 'tribe_events_title_include_cat', 100, 2);