why is my snow leopard mac speaking 'welcome to rmit' when i join a network? I did a class at a university - RMIT. 
Their network required a complex set up, which their tech support did for me.
I also set up Locomatic to switch locations when I went home and used my home network.

Every now and then, when I join my home network, my laptop says in a synthesised voice 'welcome to rmit'

Locomatic is now disabled, and I have deleted all the RMIT network and location details. 

I've called rmit tech support but they claim to have no idea whats going on.
I've given up on RMIT tech support being part of a solution.

Any suggestions where I could look to solve this?

I have growl installed, the only other non apple sys prefs are mysql, flip4mac and Tex distribution. It could be a script using the say command, but as the voice is quiet and happens unexpectedly, I've never managed to listed to it carefully enough to confirm it is one of the apple voices and not an audio file.
Something is running a process when you connect to your home network. You said "Locomatic is now disabled" - have you actually uninstalled it?  Probably worth a try.  Here's the Manual.

You might also lay a trap for say by temporarily renaming /usr/bin/say to sayx, writing a wrapper script in /usr/bin called say that calls sayx and passes its arguments to it, but which doesn't exit when sayx returns.  The next time your system speaks up, you can look at the process list with ps -f or Activity Monitor and trace through the Parent Process IDs to find out who launched what, leading to the announcement.  In fact, I'd probably do this first to make sure I know about everything that might need cleaning up.