For some reason, Comcast doesn't keep its online cable box channel lists up to date.
And they don't choose to list QAM channel assignments, not even those they must legally provide (see http://www.ehow.com/how_5417083_hd-c...s-comcast.html
on how to receive them). To a limited extant, using a QAM tuner (sometimes called a cable ready tuner) lets you see some channels you would otherwise have to pay extra to see if using a cable box.
I'm afraid if I post the actual lists on-line Comcast will get mad and change the QAM channel # assignments. But if anyone wants my list, obtained by hand over the last several days, for Prince George's County, MD (Lanham office), send me a message.