My brother-in-law works for a company that handles licensing and republishing of a lot of comic strip publishing. Lately we've been discussing the issues involved with republishing such image-based content as electronic books. (After these discussions, my wife asks "How's your sister?" and I say "Uhh, OK I guess.") I wanted to give it a shot, and found that a Google search on public domain comics got plenty of hits.
I managed to find a pretty cool one called the Blue Beetle, and issue 2 from 1955 has panels that are all the same size, which helped me to sidestep one of the tougher comics-as-ebooks issues, so I created an epub Blue Beetle comic. In the epub version the images are all rotated horizontally, so it really is aimed at smaller devices that you can easily turn 90 degrees such as the Sony Reader and the iPhone. Tests by friends show that they look pretty good on each, although the images are based on scans of 50 year-old cheaply printed paper which probably had a high acid content, so it's not as crisp as it might be. Text on anything but a white background is difficult to read on the iPhone.
Still, overall, it's pretty cool. Check it out yourself and let me know what you think.