If you have ever had to consult Abramowitz and Stegun’s Handbook of Mathematical Functions with Formulas, Graphs, and Mathematical Tables you will know what a useful resource it is. Despite its iconic status, its format and layout looks dated and its searchability could be better.
The Digital Library of Mathematical Functions project is an ongoing effort to perform a complete rewrite of this work, updated for current needs. This resource will be published in book form as the Handbook of Mathematical Functions as well as a free online Digital Library.