If you pass an array to the update_option it will automatically serialize it. you can later retrieve them back into an array like this.

    $tempoptions = get_option("plugin-options");
    if (!empty($tempoptions)) {
    	foreach ($tempoptions as $key => $option)
    		$options[$key] = $option;
    }

	

then do something like var_dump (`$options`) this will show you the entire array.

I think they use the maybe_serialize/maybe_unserialize/is_serialized functions from the codex, but I never really looked into it. Just found them now. 
http://codex.wordpress.org/Function_Reference/maybe_serialize