The Jargon File (version 4.4.7, 29 Dec 2003):

web toaster
 n.

    A small specialized computer, shipped with no monitor or keyboard or any
    other external peripherals, pre-configured to be controlled through an
    Ethernet port and function as a WWW server. Products of this kind (for
    example the Cobalt Qube) are often about the size of a toaster. See 
    toaster; compare video toaster.