The bob is a classic. For an updated, chic version, try something like Laguna Beach star Kristin Cavallari. This cut can actually be worn straight or with waves (see Rachel McAdams above). The bangs can be put the side or pulled back with a front-bump with a clip for a night out. The choppy layers add youth and spunk to a classic do.
For a more sophisticated, non-choppy version of this bob, check out Katie Holmes.