Wolfram Alpha Inc. has Wolfram Alpha (iTunes Link) in the iTunes App Store for $19.99 for a limited time. Deal expires December 31, 2009.

Drawing on 20+ years of development, 50,000+ built-in algorithms, and 10+ trillion pieces of continually updated and curated data, the Wolfram Alpha App is the ultimate replacement for almost any kind of calculator or reference book—and much more.

The breakthrough technology of Wolfram Alpha for the first time lets you get expert-level answers to your specific freeform questions—complete with stunning, dynamically generated visualizations and tables, and richer and deeper information than you imagined possible.