Due to the proliferation of cellular phones and walkmans it's not quite common in our days to take care of a quiet environment. Anyway I want to give some recommendations for the polite ones.
For the console setterm -blength 0 and for X11 xset b off turns the bell off. See also PCMCIA-HOWTO, and much more details in the Visible-Bell-mini-Howto by Alessandro Rubini.
When starting your laptop with PCMCIA-CS configured correctly, this will be shown by two high beeps. If you want to avoid this put CARDMGR_OPTS="-q" into the PCMCIA configuration file, e.g. /etc/pcmcia.conf for Debian/GNU Linux.
To avoid the dialtones during the modem dialing add
module "serial_cs" opts "do_sound=0" |
to /etc/pcmcia/config.opts (from man serial_cs). This will disable speaker output completely, but the ATM command should let you selectively control when the speaker is active.
You may configure vi with the flash option, so it will use a flash in case of an error, instead of a bell.
For at least one laptop series, the Toshiba models, there seems to be a Linux package available to control the fan and other features.