I have a couple of ways to share my music at outdoor parties or the beach. My friends here in Cleveland know it's a given that I'll be bringing the tunes. If it's a party I usually bring along a guitar practice amp. They're loud and compact. I do need to plug them into AC power and my iPhone/iPod/iPad is tethered with a mini to quarter inch cable. That presents limitations.
More convenient but not as loud is the iMainGo. You simply place your iPod or iPhone inside the device. It reminds me of carrying around a transistor radio as a kid. I love it and get compliments on it all the time.
Now comes along a larger portable music player from Eton, appropriately called the Rukus. Think of it as a modern day boombox. What's really nice is that it operates via bluetooth so there's no cable to connect to your mp3 device as long as that device is bluetooth enabled. It's also battery powered. Or you can spend another $50 and get one that's solar powered. At $100 for the non-solar Rukus it's fairly priced.
Both of these products fit my lifestyle perfectly. I wouldn't be without one whenever I head outside for some fun.
If you have a question or if I may be of service email me at radiohannibal@gmail.com
John Hannibal