Usability 
Not to be outdone by WikiPedia, the venerable Encyclopedia Britannica now has a mobile site. The search works well and the well written articles cover most topics in considerable depth and are nicely organized for mobile with navigational links to sections of the longer articles.Content seems a little on the thin side though. I couldn't find many of the topics I searched for including "Nokia", "nonogram" and "PHP", all of which have extensive entries in Wikipedia. Source Taptu Touch Web Report (PDF).