Over the last couple of months I've been using Blueprint CSS framework with the web applications I'm working on.  I looked at several CSS frameworks, but this one seems the best fit for my needs and the more I use it, the more I love it.

Here are some of the resources that I've used when learning about Blueprint and find myself referring back to from time to time.

Blueprint on Google Code - The official version
Links to Blueprint Resources - Great collection of examples, tutorials, and tools
Blueprint PDF Cheat Sheet - Single page cheat sheet contains all the classes you need to know about when working with Blueprint
Hands on with Blueprint - Great blog post with various examples

Using Blueprint, I was able to skin this this site in a couple of hours from scratch.