Here are two links I reference pretty frequently. Wanted to share them because others might use them if they are ever trying to edit CSS.
For the old 2007 version: http://sharepoint.microsoft.com/blogs/zach/Master%20Page%20Cheat%20Sheet/Forms/ViewAll.aspx
For the 2010 CSS Classes: http://erikswenson.blogspot.com/2010/01/sharepoint-2010-base-css-classes.html
They have been very very helpful to me when editing classes. If anyone has a better resource, please be sure to share in the comments!