Crybaby the semi feral cat poses next to the Grain speaker for size comparison purposes.
I have quite a few different bluetooth portable speakers. The Packable Wireless System from Grain Audio is my favorite. It's easy to operate, sounds wonderful (great bass), and has a long battery life (it recharges with a USB cable and charger, which are included). And with its walnut shell, it's also the best-looking portable powered-speaker I've seen. I can't think of a better way to listen to the streaming music on my WFMU Radio app.