CD-Romix sells comic books in CD-Rom format, I think. Actually, it's slightly unclear because nowhere on the site that I can find does it specify the format of the comics you might purchase there. The site describes itself:

CD-Romix is an electronic publishing company designed by artists for artists as a more feasible alternative for them to publish their work.

So far, you can purchase issue 1 and 2 of a comic entitled "27" by Dan Jaaren. All in all it looks like a promising new entrant to the online comics marketplace.