miketinte wrote:
I want to overlay an image or text (perhaps through CC programming?)
on all channels of my home's cable system (NTSC). What's the simplest
way to do this? Has anyone done something similar to this before and
can offer some sage advice?

Sort of...

http://www.decadenet.com/bob2/bob2.html
$79.95 each.
You program the text from your computer's serial port.
You would put one on each TV after the cable box, because it
has to work on baseband video not RF. I think this is the
simplest way and much cheaper than trying to do something with
each RF channel.
-Dan Barlow