>   I am looking for a source of keyboard controllers for
> a friend.
>
>   Basically it would be a PIC or 8051 or AVR that
> scans a membrane keyboard and sends the keys back
> as RS-232 data to some host. Probably a 4x4 matrix
> would be fine.
>
>   I would like to find a source of pre-programmed,
> documented chips (or small PCBs), and it seems that
> someone out there was making them.

Check out "MemKey" at Solutions Cubed:
http://www.solutions-cubed.com/

It does all sorts of neat things and will save you gobs of time.
Cheers, Bob