softwareupdate --list
When you log in, you'll see:
Welcome to Darwin!
Software Update Tool
Copyright 2002-2003 Apple Computer, Inc.
Your software is up to date.
www:~
To install an update if softwareupdate finds out-of-date packages, type softwareupdate -install packagename
The only drawback is that it will run each time you open the terminal, locally or remotely. Alternatively you can just run the command in the shell if it gets too annoying. Works on both 10.3 server and client. For further description of this tool, type man softwareupdate.
[robg adds: We covered the basic softwareupdate command in an earlier hint ... this hint works just fine on non-server, too. i ]

