Styles for grid-based layout, layout.css, (awesome), a comprehensive "browser reset", reset.css, with reasonable defaults for typography and spacing, typography.css. Also, some form styles and a good foundation for a print stylesheet. All in all, it's a great base.
Quick reference for Blueprint CSS.
Ooo-wee! My brother and sister gave me a homebrew equpment kit from Monster Brew for my birthday. It comes with a handbook, but this look like it might be a good additional resource -- until I can get my mitts on a paper book.