SpaceMagic said:
You could manually drag this script into everyone's "startup" items. But yes, that's time consuming. There is a folder in the Main hard disk's Library called 'startup' items. This way, I think it'll run everytime and for everyone. However, I haven't tried this but there is nothing stopping you. If your computer doesn't start up hold down "shift" when booting (and it'll disable the startup things then you can delete it).
Don't put things in StartupItems, that is for housekeeping and system configuration scripts needed by Mac OS X that only run during the boot process.
Also since only Admin users can set startup items, if you make an AppleScript application that is editable as a startup item you may create a security hole.
Save the AppleScript application as Run-only always.
If you wanted to show the user's account name as part of the AppleScript without having to make separate apps for each user try using the "MacPack Toolbox" Scripting Addition (free):
http://www.exittoshell.com/products/
It is a bit more involved, you have to place the Scripting Addition component into a folder that probably hasn't been created yet (in /Library/ScriptingAdditions so all user's AppleScript app can access it) in Mac OS X. There are instructions with the file.
Then simply make the line in the script similar to:
display dialog "Welcome " &
MP Long User Name & " to the lab." as string
Obviously make it however you want, there are other options as part of "MacPack Toolbox" including getting the computer's network/Rendezvous name, custom date formatting and simply text find/replace.
This will work on OS X 10.1, 10.2, 10.3 (I just tried it on 10.3.3).