Locally served software
Postfix “StartupItem”
Extract in /System/Library/StartupItems. Edit /etc/hostconfig and set “MAILSERVER” to “-YES-“. This is no longer required for Panther and up!
LockTight
(70 kB, including source code)
This is a stripped version of SleepTight for Mac OS X Panther (PPC).
Several people have posted an intel or universal binary version. I have not compiled these myself, so NO GUARANTEE: