Let me just start off by saying that Wolfram Alpha was $49.99. Obviously, nobody was biting, so they’ve lowered the price to $1.99. Honestly, though? The amount of information available on this iPhone app is astonishing. Though I never would have known that if the price had stayed so high.
Via a slew of categories including Mathematics, Physics, Engineering, Earth and Life Sciences, Words & Linguistics, Sports & Games, Music, etc., Wolfram Alpha is more than a mere engine that knows how to find facts. It helps you figure out how to search for things you didn’t even know you needed.
Tapping on each category displays examples of how to search. Would you like to compute properties of an elementary cellular automaton? No? Well if you did, Wolfram Alpha would do it for you.
How about a comparison of "Naked Lunch" to "On the Road?" A chart that includes author and publishing information is displayed, as well as various links, including a link to the source of the information (take that, Wikipedia. Although, links to Wikipedia entries on each book are provided).
You can bookmark/favorite the info, open in Safari, or share via email or Twitter.
Much, much more than an encyclopedia or a search engine, Wolfram Alpha is a comprehensive informational and computational database that provides meaningful results. Even if you don’t know what they mean.