You're quite right that in this long bullish moment, there's a certain hollowness and lack of commitment to big ideas and grand movements--at least among liberals! For example, the vice president's livability agenda picks up where many of the president's popular small initiatives (community police, smaller classes) leave off. But let's not forget that we've heard a lot of large ideas in recent years from conservatives, and that some of them have had real political or legal influence.
Take anti-federalism for one--or the idea that the balance of power ought to be shifted away from Washington and toward the states. Sixty-some years after the New Deal, the Supreme Court has taken some serious cuts at Congress's authority to enact federal laws that were once taken for granted. It struck down a federal no-guns-in-schools law as too unrelated to commerce, and struck down the Religious Freedom Restoration Act as too unrelated to enforcing anybody's real religious-freedom rights against the states. Just recently, the Fourth Circuit--the federal appeals court for Maryland, the Virginias, and the Carolinas--invalidated the Violence Against Women Act, which allows people to bring federal lawsuits for damages for gender-motivated violence. The court held that the law neither governed interstate commerce nor enforced anybody's civil rights against the states. There's a good chance the Supreme Court will affirm.
Or consider the anti-affirmative-action movement, which trades on the rhetoric of color-blindness it has plucked selectively from the work of the civil rights movement itself. California's popularly enacted Proposition 209 illustrates the political potency of this movement; lawsuits against racial preferences in admissions to the public law schools at Texas, Michigan, and Washington illustrate its legal persistence. Again, big idea, activist movement. (Of course, it's an idea that ignores that the civil rights movement was devoted to ending a socially entrenched system of racial hierarchy and subordination--something affirmative action cannot credibly be thought to create.)
So, liberals and progressives are often cast in the role of rear-guard defenders of a New Deal or New Society status quo. No wonder the arguments are often small-bore or pragmatic. Bowen and Bok's recent magisterial defense of racial diversity in university admissions, for example, emphasizes that it makes society work better, not that it is the embodiment of a grand idea.
Now, let's not forget that conservative grand ideas can go down in flames, too. The Contract With America is not in much better shape right now than the Berkeley Free Speech Movement. (Term limits? Balanced-budget amendment? Stopping those flag-burners? Newt Gingrich?). But I'm curious what you think might spark grander ideas to galvanize the left, other than an ambient sense of spiritual hollowness amid affluence.