My book Mathematical Constants is now available for online purchase from Cambridge University Press (in the United Kingdom, North America and Australia). It is far more encompassing and detailed than my website ever was. It is also lovingly edited and beautifully produced - many thanks to Cambridge! - please support us in our publishing venture. Thank you. (If you wish, see several very kind reviews. You can also search the book via Amazon and Google by keyword.)
Here are errata and addenda to the book (last updated 9/27/2013), as well sample essays from the book about integer compositions, optimal stopping and Reuleaux triangles. Here also are recent supplementary materials, organized by topic:
Here are several favorite links: Mathematical Constants and Computation (by X. Gourdon & P. Sebah), MathWorld Constants (by E. Weisstein at Wolfram Research), the Inverse Symbolic Calculator (originally by S. Plouffe & the Borwein brothers), and the On-Line Encyclopedia of Integer Sequences (by N. Sloane).
Here finally is contact information for me. I appreciate your interest!
* In October 2002, an ex-employer demanded that this website (formerly at INRIA) be shut down, and I had no choice but to comply (lapsed links here & here). I am grateful to Cambridge University Press for patiently seeing me through a difficult time (up to June 2003).