What classic hardware/software companies were most
famous for this?  I've
 learned (from Allison and Megan's various posts) that Digital sometimes used
 other companies' stuff -- often at the cheap end of a line of products, I
 suspect.  What about IBM? Wang? Microsoft? 
I think you will find that near EVERY company has done this to some point.
Example - IBM System/88s are actually Stratus machines.
William Donzelli
william(a)ans.net