You can use the native wordpress Tag Cloud widget and set the taxonomy to speakers. It works but WordPress natively limits the number of items in this tag cloud. I'd love to see a Speakers widget in the plugin that gets around the limit and allows us to put on some other filters. I do an interview based podcast and have some recurring guests and 1-timers. Right now the 1-timers are filling up my quota and I can't show as many repeat guests.