Out of Ur has a good two-part essay asking how Christians should understand the call to do justice (link goes to part 1; here's part 2). The suggestion? Christians should focus on local, person-to-person justice as a part of their everyday faith, rather than treating it like a political concept or a special church program:
If we are to avoid making justice into another program in the church we must resist the urge to make justice primarily about national politics, and only secondarily about local politics. For inevitably we get caught up in national politics believing that finally we are doing something. This then becomes an easy program to establish in our churches, and the work of local justice becomes an after-thought because political activism is always easier than living as a presence with the poor. It may be admirable and glamorous to help Jars of Clay fight Aids in Africa or Bono fight for Third World Debt Relief, but in the end I would ask us how much is accomplished if we cannot witness to a way of life that compels justice in our own back yard.
Justice is something we can do in our day-to-day lives, not just something we practice by supporting the correct politican or giving to the right charity. In fact, talking about justice as primarily a political issue can be more harmful than helpful, as it tends to get bogged down in the tired old "right. vs. left" political debate. It also tempts us to think of justice as a "program" rather than an integral part of our Christian life.
I particularly like that last point: promoting Biblical justice isn't an optional, extra activity that is only performed by trained ministers or special political organizations; it's something that's part and parcel of a Christian's life. (It's a point similar to the one made about the m-word in Mikey's post earlier today.)
On a closely related note, earlier this week I stumbled across an article at Youth Specialties called Jesus Justice: So Easy a Five-Year-Old Can Do It [PDF]. The point there is that justice isn't abstract and difficult; it's something we can all understand and put into action.