ezmlm ("Easy Mailing List Manager", not to be confused with MLM
) is a mailing list manager
program that has quickly become a serious competitor to Majordomo
... It's based on qmail MTA
, and was written by Dan J. Bernstein
It has all features you can expect from a mailing list handler: subscription handling, archival, bounce handling and such.
Personally, the only thing I've found annoying about it is that it looks at the real address by default when subscribing, not at the From: address (I guess this is to make listbombing harder). This is a pain in the neck sometimes.
Home page: http://www.ezmlm.org/