Self-initializing quadratic sieve (SIQS), on a 2GHz Opteron, a 95 digit factorization takes 4 hours, and a 100-digit factorization takes just under 12 hours (possibly more). Public domain library for integer factorization, implementing Pollard-rho, ECM, self-initializing Quadratic Sieve and parts of NFS.
On 2022-06-21, the original page http://www.boo.net/~jasonp/qs.html is off-line: "All Delmarva Online services have been discontinued. December 27, 2014"
With the help of http://web.archive.org/web/20110723030828/http://www.boo.net/~jasonp/qs.html, I could locate the repository https://sourceforge.net/projects/msieve/files/msieve/ which has been updated 2016-11-11. I changed the URL for the bookmark to the sourceforge repository.
A book introducing basic concepts from computational number theory and algebra, including all the necessary mathematical background. Available as PDF under a creative commons license and as book from Cambridge University Press. (Recommended by Mark Wooding).