When I do free seminars on getting into college, I don't usually mention class rank. It's not that colleges don't care about it, but I know that there will inevitably be a family in the audience who is already upset about their high school's ranking policy. Some schools issue a numerical ranking ("You're number 4 out of 122 seniors); some schools don't. And it seems that no matter which policy a school chooses, there will be students who feel the choice will put them at an admissions disadvantage.
I wrote a past post about this, but if you don't believe me, see this recent entry from the University of Virginia's blog. The class rank is just one factor. If your school ranks, a college may use your rank as one factor of their evaluation of you. If your school does not rank, the college will find another way to evaluate your performance in relation to that of your fellow seniors.
This comes back to one of my overriding themes for this blog–focus on what you can control. You aren't in charge of whether or not your school ranks. So let that go. What you can control is the rigor of your course selection and the effort you put out to get good grades. Don't get rankled about the rank.