The Encyclopædia Britannica has been released on iOS for the iPad and iPhone. For $1.99 / month you get access to over 80,000 articles which looks like a good deal, unless you believe that Wikipedia is just as good.
*Search & Browse:
Over 80,000 articles – expertly written and thoroughly fact-checked – on everything from A-Rod to Zebras. Our contributors include over 100 Nobel Laureates plus subject gurus like Bill Clinton, Tony Hawk, and Desmond Tutu.
Photographs, diagrams, and charts help bring each topic to life.
“LinkMap” lets you explore each article with a dynamic view of related topics.
“My Britannica” keeps track of your favorite articles and more.