I've been using iComic, and loving it. Dude seems to be constantly improving his program. Recently he added an FTP server so that you can move your comics to the device using wifi FTP. Excellent.
Excellent source of public domain comics here:
http://goldenagecomics.co.uk/index.php
For Linux folk I've made a nice bash shell script for converting the large hi-res cbr/cbz files into something more suitable for my Ipod Touch. More info here:
http://my.opera.com/ligelowbee/blog/...uch-icomic-app