Cadence is a CSS library for setting vertical rhythm. It handles line-height, margins, and a few instances of padding. I've tested it quickly in Firefox, Chrome, and Opera and it seems to behave quite consistantly. I haven't tested it in IE, and I'm not sure I care to. I probably will eventually, but it isn't a priority.
By default, Cadence uses a font-size of 16px and a line-height of 22px, though all sizes are in rem and can be adjusted easily from the src/cadence.scss file.