WSRP 2.0 is out since june. WSRP is certainly worth a look, but by its intention, it defines only portlet-specific CSS selectors (portet-font, portlet-menu-*, ...)
a superset of WSRP is defined by the jboss portals, which is real-world proven:
http://docs.jboss.org/jbportal/v2.6/reference-guide/en/html/
aside of css selector, we need a design or vision or style guide, how css files should be organized, what's a core-framework issue, what's a oacs-package issue and what's a page or page-fragment (portlet) issue, and how to influence this from a single point, a theme...
