Windows NT

Ah Goeie
A front-end graphical interface to the Net Send command in Windows NT/2000. Used to send messages to a group of users or a single station.
http://www.digital-kingdoms.net/ah-goeie/

BackLog
Facilitates the real time central collection and processing of event log information.
http://www.intersectalliance.com/projects/BackLogIIS/

ND Telnet Server
Small telnet server that runs as a service.
http://hem.passagen.se/deschatr/ndtelnet.htm

Nick Rozanski: SrvStart
A Win32 executable and DLL which allows you to run commands as if they were Windows NT/2000 services. The DLL can be used on its own to build a service without having to write any service management code.
http://www.nick.rozanski.org.uk/

RShut
Utility to remotely shut down and reboot networked computers
http://www.rtsecurity.com/products/rshut/

WinIPDO
Utility to execute any command when your IP address changes.
http://www.flaredev.com/