The first zombie comic and one highly remembered and loved by fans is Deadworld. They are doing a 5 issue mini series right now. It has been published sporadically over the years, but originally came out in the 80s. Some of the series is collected as trades and there is a DVD-Rom out there with a good chunk of the series in PDF format.
This is a fun book I picked up recently.
And, of course you've heard of a little book called Walking Dead as well.