Web Administration
See NODOWS Webop Administration.
Proxy Configuration Machine
For systems with extremely tight resource constraints, I'm thinking about something like openssh with keys, rbash, and sudo for remote administration. For example, a web server running on a more powerful machine could provide the user interface and interactivity to logically configure a target device, and then the configuration could be processed and sent to the target device. Obviously security and sanity checks are of utmost importance.
Console Administration
I like the m0n0wall approach of having a simple console with very limited configuration options. For production systems, I'd prefer use of the console to configure the host, and then use web configuration for the virtual environment. This way the host environment could be very secure, simple, and small.