BCP for Private OUI / address assignments?

[mike <mike-nanog () tiedyenetworks com>]

   With the increasing use of virtual machines in my environment, I am 
needing more and more unique mac addresses to assign to the many virtual 
Ethernet devices I have attached and visible to my non-virtual physical 
network. The problem of course is that I don't have an IEEE OUI and 
therefore can't generate guaranteed to be unique addresses, and while 
the possible address space is quite large, it occurs to me that there 
should be something - ala rfc 1918 - for this kind of situation. For now 
however, I just want to know if anyones got something better than 'pick 
an oui out of the air' or 'pick an old dead manufacturer oui', or worse, 
'pick old 10base2 network cards and destroy them, saving the mac'. In 
the future however, I think there's going to need to be some sort of 
extension or modification to dhcp to accomodate virtual machines in this 
regard (of not having a manufacturer assigned addresses for the virtual 
ethernets).

Mike-