You can find the MAC address of your system at the command line by using the ifconfig command. The ifconfig command will show you information on all your network interfaces. If no arguments are given ifconfig displays the status of the currently active interfaces.
You have to run this command as root or use sudo.
# ifconfig
wlan0 Link encap:Ethernet HWaddr a1:b2:c3:d4:e5:f6
inet addr:192.168.2.11 Bcast:192.168.2.255 Mask:255.255.255.0
UP BROADCAST RUNNING MULTICAST MTU:1492 Metric:1
RX packets:4007 errors:0 dropped:0 overruns:0 frame:0
TX packets:4246 errors:0 dropped:0 overruns:0 carrier:0
collisions:0 txqueuelen:1000
RX bytes:3292271 (3.1 MiB) TX bytes:994922 (971.6 KiB)
Your MAC address is displayed in the HWaddr field.