For shear volume, The Block Rocker by Ion. Costco has these on sale for $120. I have one I take to the beach, drowns out the wind and the waves.
http://www.ionaudio.com/products/details/block-rocker-am-fm
thanks for this recommendation and putting these speakers on my radar.... when I eventually found that my local Sams Club had them for the same $120, I went down there and they had both the Block Rocker AND Job Rocker for that price, so I sat there for like 10 minutes debating the pro's and cons of each.... since I'll mostly be using it around my house and out on the deck, I decided that the 2 AC outlets in the back of the Job Rocker trumped the USB outlet on the Block Rocker, and I'm glad I made that decision.... I can stream my Mac directly to it via Bluetooth, but that makes the speaker the only playback audio device... many times, I'm in and out and when I step inside, I can no longer hear the music being streamed out on the deck, but I realized I can just plug one of my "Airport Express" receivers directly into the back of the Job Rocker and use a patch cable to make it another component of my wi-fi network audio "network".... so now I've basically got my whole house and deck wired for sound to the Mac, thanks to that little Job Rocker....