I also use Blueprint, I find it to be easy to pick up, simple to use and makes doing page layout a breeze. I would also suggest looking into jQuery UI's built

I also use Blueprint, I find it to be easy to pick up, simple to use and makes doing page layout a breeze. I would also suggest looking into jQuery UI's built in CSS / Theme Roller stuff. I've worked on projects using blueprint to lay things out and jQueryUI to style widgets and it has worked out really well.