Heather has done some great work again when it comes to CSS and SharePoint (V3). Check out her reference chart for the classes and property overview.
"The following CSS reference guide highlights the major styles used in MOSS and WSS v3 sites. The guide is organized by area of the page and include the style name, function, CSS file name and approximate line number and a sample screenshot of the style location on the screen. Use these guides to identify styles that can be overridden for your custom branding and installation or to quickly reference style name and CSS information for customization."