Best portable/outdoor speakers for a MP3 player

Hi I'm looking to buy some speakers for my MP3 player. Idealy they would be portable as it would be used buring BBQs and parties in the garden. Any suggestions as to which speakers would be best.
B&W used to make a Rock Solid for outdoor use which was very decent and now very cheap used.
ipodlounge is a great source of reviews and recommendations for speakers and other accessories. It's iPod-centric but virtually all of the speakers accept output from any mp3 player via the headphone jack. There are two categories you might be interested in on that page, Speakers-All-in-One/Portable and, for larger ones, Speakers-All-in-One/Room-to-Room.