The market for portable Bluetooth speakers is growing more competitive by the day, with various manufacturers spitting out the rectangular prisms in a wider variety of sizes and price points. But generally, this increasingly common accessory comes in one of three form-factor flavors.
First, you have the Jambox-sized devices. Definitely carry-aroundable, but not necessarily something you'd keep in your bag all the time. Then, you have the not-really-actually-portable, but "portable," Bluetooth speakers.