Susy looks to be a very nice tool for making cleanly marked-up grid-based sites. It’s one of the many new compass plugins that are floating about these days. It doesn’t claim to be an out of the box layout, and that’s what makes it such a strong candidate for a real life solution.
From the start, Susy is highly configurable. This means you’re not stuck with a column count that is tightly coupled with your grid system (I’m looking at you blueprint). This leaves designers unburdened with a bunch of mundane math, while still free to use uniquely appropriate grids. The project can be found at https://github.com/ericam/compass-susy-plugin