CSS Peeper - Smart CSS viewer tailored for Designers.
Pressbooks - Create books: print and ebooks
CSSViewer - A simple CSS property viewer
Papermine - Create stunning digital booklets.
CSS Dig - CSS Dig is a Cascading Style Sheet viewer extension that allows you to collect and style the website element properties.
Mockupea - Mockupea is an online tool for creating 3d book mockups with a lot of features.