Obtain some basic hardware details of your Ubuntu system

Unix systems are capable of recognizing lots of details of your hardware, so instead of having to open your PC for obtaining information like serial numbers, just use some shell commands.
Here is a list of such useful commands.

General system

grep -r . /sys/class/dmi/id/ 2>/dev/null
lsusb
lspcmcia
lspci -vvnn
udevadm info --export-db
lshal
sudo lshw

BIOS

sudo vpddecode    # Serials from BIOS, Motherboard
sudo biosdecode   # More details about BIOS
sudo dmidecode -q # Show information about valid BIOS components
sudo dmidecode    # Show also unknown/invalid BIOS components

CPU

lscpu
cat /proc/cpuinfo

Audio

cat /proc/asound/card*/codec#*

Drivers

lsmod