MACmonster is an online tool that allows you to lookup the vendor of any MAC address or OUI.
Examples "BC:30:5B:00:00:1A", "BC3.05B.000.01A", "BC-30-5B".

What is an OUI ?
An OUI is a 24bit number that identifies a vendor, manufacture or organization and typically forms the first 24bits of a MAC address.

What is a MAC address ?
A Media Access Control address (MAC address) is a unique identifier assigned to network interfaces for communications on the physical network segment.