Jurgen Habermas, some links.
A quick overview of his Critical Theory
From Representative Publicity to Public Sphere
Habermas links, Habermas rechts you need to read German to both appreciate this clever title and the site with the mixture of quotes in German and English.
Habermas and the Frankfurter school, and despite the consistent use of "was" in this article, Habermas is not dead and his contributions to scholarly thinking are still at the "is" stage. The rest of the Frankfurter school can be spoken of in past tense though.
More Habermas resources.