CSS Pseudo Classes
CSS3 has been floating around out there for a while but it still hasn't gotten a foothold - which is unfortunate. One feature that will change the way you think about your CSS is support for massively more-powerful pseudo-classes. Currently we stylers are limited to :hover
and in most cases :first-child & :last-child
If you regularly use jQuery or at least look through the docs you know that there are some other pretty powerful options that would make some of CSS sweater.