It may not be a perfect calculation, and they might not be my full-time personal slaves, but isn't even one a slave too many? As the world is now, it's next to impossible to be 100% "slave free," but we can definitely reduce our dependence on slavery by paying attention to our purchases.
slaveryfootprint.org. Go find out how many slaves are working for you and take a few minutes to check out the methodology they use.
They also have a "take action" app you can download for iphone or android. Because, of course, consumer driven action is the important part. I just downloaded it, so I don't have a review, but I love the concept.