It's not as if you can see the vendor simply by looking at the MAC address, since it's only a number. Each vendor has bought one or more range(s) from the appropriate authority (IEEE).
here's the latest complete list:
standards.ieee.org/regauth/oui/oui.txt
and here's a service for looking up for specific vendor or ID assigments:
standards.ieee.org/regauth/oui/index.shtml
Of course with all the buys, cooporations and sells one can never be sure.
