It's almost always the "hash key" here in Ireland.
One of the phone companies here will go as far as saying "... and press the hash key, located under the number 9 on your telephone keypad"
Some US systems also call it "number sign"... and I remember a Sony answering machine that insisted on calling it "gate" in voice prompts.
I remember using some very old telecom service that asked you to "key your ID number and terminate with a hash!" How customer friendliness has improved!
The same system liked to tell you "your call will now be terminated"
....
There's now the much more patronising:
"Are you still there?"
"you appear to be having difficulty...please try again later or call our helpdesk on ..."
[This message has been edited by djk (edited 04-22-2005).]