A quickie to remind myself next time I build an Ubuntu box, and am being slowly driven batty by a tiny, tinny obsolete PC speaker made of hate:

sudo gvim /etc/modprobe.d/blacklist

(or /etc/modprobe.d/blacklist.conf, for Ubuntu 9.04) …and add the following line:

blacklist pcspkr

From the command line, kill it in the current session:

sudo rmmod pcspkr

No more waking the baby with late-night hacking sessions!