Madrid pointed out the Blueprint CSS Framework to me the other day and I was disappointed that I hadn't heard of it before. The thinking behind it is to provide a solid grid based system of pre-configured CSS styles to help quickly develop a site. Added to that is the fact that loads of developers are working on making the whole thing even more dynamic by providing apps like this Grid Generators so it can fit any project. There are also handy cheat sheets to get you started. While it's obviously something that you deploy from the start of a project I think it's well worth looking into.