Björn Engelmann, Joachim Posegga, and LocalRodeo developer Martin Johns have authored an excellent paper on a new Cross-site Scripting detection system called XSSDS.  Stay tuned to noxss.org for a new browser extension based on this technology.  The XSSDS approach is similar in some ways to the IE8 XSS Filter approach, although it's worth noting that until recently Martin's team had no knowledge of our work in this space (and vice versa).