There's a huge range of Bluetooth speakers out there to chose from, but the choice is pretty easy when it comes to Ultimate Ears' Wonderboom.
At $100, the Wonderboom is small, light, waterproof, durable, inexpensive, and it sounds good. You can take it anywhere to deliver music in pretty much any situation.
It won't blow you away with its sound quality, but it's still pretty great considering its size and price tag, and it's plenty loud to boot.
Check out the Ultimate Ears Wonderboom:
Ultimate Ears' Wonderboom is a small, lightweight Bluetooth speaker you can bring anywhere.
The Wonderboom is about the same size and weight of a softball. It doesn't take up much room on a table or anywhere else you want to put it. It's also light enough that you can easily carry it by the tiny strap with your pinky. Anyone who carries outdoor stuff out, and then back in at the end of the day, will appreciate that.