Hi Jon,You're right - you plug the speakers into the headphone jack on your Book Port. It's best to use speakers that either have batteries or run on AC power. I got some at Walmart recently for around U.S. $25 - two small speakers with a cord connecting them. They run on battery or can be plugged in. Sorry I don't know the model, but they're very nice. There was an all-in-one unit that was really cute for maybe $10 more than that. Any set of speakers designed to work with MP3 players should work unless they're specifically designed to work with an iPod or some other player that has a special dock connector. Be sure they will work with a headphone jack, and you should be all set.
Cheers, Anna