Just south of Santa Monica is Venice Beach, a more alternative option. Walk down the boardwalk and you will find a panoply of California's hippie-esque culture. From street vendors to guitar wielding roller bladers, this beach is a circus of people and a sight to see. After a relaxing day at the beach, check out the street performers or just sit outside a restaurant and watch the sunset. This beach definately models California's laid back atmosphere.
For the nightlife in Venice, walk to Abbott Kinney Boulevard. Here you will find gift shops and boutiques along with bars and restaurants. A more low-key, upscale contrast to the beach it is so close to.