qmail
http://www.qmail.org
Dan Bernstein's qmailen-usqmailhttp://www.qmail.org/Q.6.01.Logo.small.jpg
http://www.qmail.org
Davide Giunchi has written an Italian qmail HOWTO
http://qmail.org/top.html#200101070
Jesse Sweetland has written checkpassword and qmail-getpw replacements with MySQL support.
http://qmail.org/top.html#200101050
(also available as a news channel
http://qmail.org/top.html#200012280
Michael Elkins has a tool to synchronize a maildir with a remote IMAP mailbox.
http://qmail.org/top.html#200012230
Jay Soffian has a qmail-queue replacement to filter against DNS spamlists.
http://qmail.org/top.html#20001230
The qmailanalog package analyzes qmail log files in various ways.
http://qmail.org/top.html#20001227
Ismail Yenigul has a qmail log analyzer tool
http://qmail.org/top.html#20001223
Sean Truman has some mrtg scripts
http://qmail.org/top.html#20001223
Bruce Guenter also has written ucspi-proxy
http://qmail.org/top.html#20001214