I've heard of a bunch of brides getting their bridesmaid dresses from J. Crew, but they're pretty expensive. - http://www.jcrew.com...id/dresses.jsp Another option is ModCloth (I work there and we sell to a lot of wedding parties) - http://www.modcloth....es/Party?page=1 but you have to mobilize fast - we only carry a few of each item, so things can sell out quickly.
Beachy doesn't have to mean blue and pink. It's your wedding, and you can put a beachy spin on whatever color combo you like best...just be imaginative, and don't be afraid to spray paint! Black glossy seashells or driftwood and ivory candles? Yes please!