It is hard to find reviews of these and most seem like junk. Monoprice does a budget set for $83, but Sound and Vision just did a review set and for not very much, you can get a nice sounding set of outdoor speakers:

• Niles OS5.5 Black (Pr) 5 Inch 2-Way High Performance Indoor Outdoor Speakers.. These were the top rated ones.
• Definitive Technology AW 5500 Outdoor Speaker (Single, White). These a bit cheaper and wall mounted